When to Solo

Jun 27 2009

Every term, without fail, I get a few assignments handed in with all of a mixer’s solo buttons enabled. The usual problem seems go something like this, “I turned a solo button on and it muted all of the other channels on the mixer. I’m not sure what happened but in order to hear my mix again I had to turn all of the solo buttons on.” As ridiculous as this might sound to a pro, it’s a common mistake for beginners. If you don’t know what the purpose of the solo button is you’re not going to understand what’s going on when you press it. So, let’s clear this up once and for all.

At its core, the solo button on a mixer channel allows you to quickly audition a signal all by itself, or with a group of other solo enabled channels, without needing to mute all of the channels that you don’t want to hear. For example, if you see a signal on Channel 10 but you’re not sure what it is because you haven’t labeled that channel yet, press the channel’s solo button. Or, if you need to have a closer listen to the blend on a three part vocal harmony, press the solo buttons on all three harmony channels and instantly mute all of the other tracks in your mix. Then, to return your mixer to its normal monitoring mode, turn off all the solo buttons. Pro mix engineers are constantly switching back and forth between listening to soloed signals and the whole mix as they’re working.

The obvious reason why you don’t want to leave mixer channels in solo mode is because you might have a channel muted somewhere on your mixer that’s supposed to be in your mix. It’s easy to hear if you’re missing something really obvious like a guitar or vocal part, but you might not so easily realize that you’re missing an aux effect return channel. For example, if you’ve soloed a bunch of tracks your reverb return channel might be muted, and, consequently, you’d be missing much of the depth and space in your mix that was being created by your group reverb effect. (If you’re not sure about how a group reverb effect works, check out my earlier blog titled, “Let’s Talk Reverb“.)

At this juncture, it’s worth noting that there will be channels you never want muted when you press a solo button. For example, if you always want to hear a soloed track with its group reverb effect intact. Or, when you have a MIDI control track that always needs to be running in the background (such as a drum track or controller data). In these situations, you never want the tracks muted when you solo a mixer channel. So, to safeguard these tracks the best designed mixers have a function called solo-safe which allows you to disable the track mute action for those channels in solo-safe mode. For example, in Digidesign’s Pro Tools you press Command (Mac), or Control (PC) and click on a solo button to enable a channel’s solo-safe mode.

It’s also worth noting that there are several different types of solo modes, dependent on the level of mixer (hardware or software) that you’re using. Top of the line pro mixers may have three or four different solo modes that you can switch between, while a basic home studio mixer usually just has one set solo mode. The two most common modes that you need to understand are latching and canceling. They may have different names dependent on the mixer’s manufacturer, but they will always operate in the same basic fashion. On a mixer with latching solo the solo button stays on until you turn it off. You can keep pressing solo buttons and they will all stay on until you turn each one off. On a mixer with canceling solo pressing a solo button turns it on and pressing another solo button turns the last solo button off. Consequently, in canceling mode you can only have one channel soloed at a time unless you hold down a modifier key while pressing additional solo buttons (such as the Shift key in Pro Tools).

I wish every mixer had, at the very least, these two basic solo modes. However, more often than not most mixers only feature the latching solo mode. And, those mixers that do have both modes are usually set by default to latching. Though, I can’t help but think that having the default solo mode set, instead, to canceling would help beginners avoid a lot of confusion. This, and Mackie’s brilliant feature on their hardware mixers, the Rude Solo Light. It’s a big red indicator that let’s you know whether you have a solo button engaged somewhere on your mixer. Indeed, novices and pros alike can use this feature because when a mixer contains a ton of channels and a solo button is accidentally left on somewhere on the mixer, especially on a channel that has little or no audio, trying to figure out where all of your sound went can leave even the best producer scratching his (or, her) head for a minute.

Mackie Rude Solo 420
photo credit: inweaknessbe’s photostream

The usefulness of a good sampler in your production toolkit can’t be overlooked. It’s great for everything from developing your own custom sounds to consolidating your favorite samples into a single instrument. Back in the 80s, dance and hip-hop pioneers could put together an entire track using a hardware sampler with just 2 MB of memory (that’s MB not GB). On it they’d have all of their drum samples, bass and keyboard sounds, even guitar phrases and backing vocals. Working this way, with just a few MIDI sound modules and very limited RAM really forced you to be creative, to write solid beats and killer songs. Unlike today, you weren’t in a position to dazzle listeners with layers upon layers of neatly produced sounds because, frankly, you just didn’t have the tools. Instead, you had to focus on the basics, where every part that you played was integral to your song’s arrangement.

There’s a lesson to be learned here. It’s such a privilege to have all this production power in our computers at our fingertips, but having all of this power is no guarantee that we’ll be able to write good music. As an exercise in my Producing Music with Reason course I demonstrate the unbridled power of Reason’s NN-XT Sampler and what you can do with it when you truly understand how to milk it for all it’s worth. Students generally find the lesson to be an eye opener, but because it’s such a different way of working and thinking about arranging it can be a confusing lesson. So, in addition to the online lesson material, and the assigned reading, I’m posting a 9 minute video that follows me through the entire process of constructing a custom NN-XT patch.

Those of us that ran up a credit card bill in the 80s buying just one Akai or Roland sampler for around $2,500, well, we were determined to get the most out of our new hardware. We had excellent incentive, we had to write a “hit” to pay off our credit card bill. There’s much less incentive nowadays, beyond the personal challenge, to write an entire track using just a sampler. But, I’d strongly encourage you to give it a try because besides the fact that it’s a lot of fun it will force you to learn a sampler inside and out and to stretch your production chops and think in new ways.

Now, here’s some incentive: Imagine if you will that you’ve been caught in a temporal vortex and transported back in time to 1982 and the only way for you to get back home is to write a satisfactorily slamming beat with your Akai S900 sampler and 2 MB of memory. Now there’s a challenge, are you up for it?

Here’s my attempt to get back to the present, written entirely using Reason’s NN-XT sampler and a few effects devices. And, just to make things even more realistic, I did this in Reason Adapted, the limited features version of Reason.

Big Samples MP3

Big Samples Reason Song File

Download directions:
Right-click PC and from the pop-up menu choose, “Save Link as…”
Control-click Mac and from the pop-up menu choose, “Save Link as…”

This blog contains very little in the way of a production lesson. Instead, it’s mostly for entertainment. However, without a doubt, there are some amazing production techniques that go into producing a great sounding mashup. I talk a bit about what a mashup is and give you an example of a mashup in a Reason song file in my blog, More Than a Mashup. That’s my take on a mashup. Now, Party Ben has taken it to a whole other level and is mashing up not only songs but the video too! Check this out, it’s skillfully done and way too funny.

By grasping the concept of velocity layers in a sampler you will be able to better use and more easily create your own dynamic and exciting sampler patches. Digital samplers, like Reason’s NN-XT, are an essential tool for creating your own unique sounds and audio effects (such as stuttering) and have been a secret weapon of hit producers since the early 80s (especially in hip-hop and dance music).

In my Producing Music with Reason course I have an entire lesson dedicated to the NN-XT Sampler. It’s that powerful and that deep to warrant a whole week of study. Yet, the assignment at the end of the week, to build from scratch your own NN-XT patch, is for many a serious struggle. Consequently, the way I figure it, I can’t have enough material explaining the finer points of the NN-XT. That said, here’s a video tutorial I did on understanding the power of velocity mapped zones in the NN-XT Sampler.

Reason Song Template

Sep 06 2008

Many students have asked me for a Reason song file template to be used as a starting point for their own projects. This sounded like a good idea to me so I’ve cooked one up that’s especially suited for most forms of popular electronic music, from hip-hop to dance. It’s not meant to be used verbatim, instead, you should modify it to your liking and save it as your own Reason song file template. It’s also pretty complex and if you’re not an advanced Reason user there may be some sections of the routing that you might not know how to use yet. Many of the techniques presented in this template are thoroughly covered in my Berkleemusic course, Producing Music with Reason.

Remember that after you create your ideal song template, you can have it loaded automatically whenever you launch Reason. This way, you’re always ready to start writing, with no time spent setting up your rack. In Reason’s Preferences, under the General tab, set the Default Song to Custom and choose your song file template. And, remember to set your song file to Read-Only. This will ensure that when you save a song it won’t write over your original template file.

Reason General Prefs

Here are some highlights and tricks (in no particular order) for using my song template and making it your own:

· Several instruments are set up as combinators. The instrument Inside the combinator is routed through compression and parametric EQ processors for mixing. To browse for any instrument while still maintaining all of the connections, find the instrument inside the combinator and use its Patch Browser. And, when browsing for patches, select the Show All Instruments option so your patch browsing is not restricted to a single device type.

· You can control either the combinator itself or the device within the combinator from a track in the Sequencer. I have both types of control tracks set up. The main advantage of using the combinator track to control a single instrument inside the combinator is that you can automate the combinator’s knobs and buttons from this track. Of course, you’d need to assign the combinator’s knobs and buttons to some device parameters for them to be active. (Keep in mind that I’m not talking about a multi instrument combinator patch here, for which you’ll always need to use the combinator track to gain control over all of the instruments inside the combinator.)

· There are several labeled clips on the Song Markers track in the Sequencer. These can be used as song markers to organize your song structure. Modify them and make your own as necessary.

· There’s a mastering combinator set up and ready to roll in the rack. Only, it’s set to Bypass because, as a rule, it’s better to produce and mix your track without monitoring your work through active mastering processors. In short, this is because the mastering processors are coloring your mix prematurely, before you’ve completed your production. Instead, save the mastering for after your mix is completed. (I’ll cover this topic in more detail in a future blog.)

· Not only are all of Redrum’s individual outputs routed through compression and parametric EQ processors, for the best control possible over each drum part in your mix, I’ve also connected Redrum’s sends to some extra parallel drum effects (a DDL-1 for delay and a Scream for lo-fi). You can use Redrum’s sends to send a drum signal to these effects before the Drums sub mixer. The effects themselves are returned on Channels 8 and 9 on the Drums sub mixer.

· I’ve set up parallel compression for your drum mix by splitting the output of the Drums sub mixer into two signal paths, one that is compressed and one that is not. Both sub mixes come up on Channels 1 and 2 of the Main mixer. This way you can easily mix in the parallel compression effect on your drums to taste.

· After the Main mixer, I set up a Sub Master mixer for some fun with global effects. The Main mixer’s output is split off to the following effects: there’s an MClass Compressor for parallel compression, an ECF-42 for that classic filtered sound, and a PH-90 for that classic phasing sound. The returns for these effects are muted on the Sub Mixer. Mix their levels to taste and automate how and when they drop into your mix (don’t leave them on all the time).

That’s the scoop. Have fun with this Reason 4 song file template.

Reason 4 Song File Template

With the introduction of Elastic Time, in Pro Tools 7.4, it’s clear that Digidesign is taking a proactive stance against competing programs boasting easy to use, time compression/expansion based, automatic beat matching algorithms. Though it’s tough to proselytize that Elastic Time is as easy to apply as similar functions in competing software applications, I can say, without a doubt, that it kicks butt in terms of its audio quality and the level of direct control you have over how the algorithm is processing your audio. It’s deep and offers a variety of ways to fine tune the processing, from multiple Elastic Audio “plug-ins” (Polyphonic, Rhythmic, Monophonic, and Varispeed), to individual control panels for each plug-in type, and the ability to freely edit Warp markers directly in the Edit window. Talk about control! Due to the simple fact that you have such a high degree of control over the Elastic Time processing, it requires a bit of homework to master, but once you do, you can achieve absolutely stunning results.

It’s important to note that Digidesign calls Elastic Audio a “plug-in”. However, it’s not applied in the way you’d normally think of a plug-in, as an insert on a mixer channel or an offline AudioSuite processor. Instead, it’s applied directly to a track in the Edit window, with its plug-in menu located just below the track’s Timebase selector.

ET Selector

Beat Matching Made Simple
Elastic Time is at its most intuitive when browsing for loops in the Workspace. Simply turn on the Audio Files Conform to Session Tempo button (it looks like the ticks metronome) in the Workspace, select one of the four plug-in types (they’re pretty self-explanatory), and when you click on a loop’s play button (the little speaker) the loop will be automatically analyzed and played back at your session’s tempo. You can even do this while your session is playing, allowing you to hear immediately whether the loop you’ve selected is a bang or a bust. Talk about optimizing your workflow! When you find the loop that you want, simply drag it into the Edit window and it will be deposited on a newly created ticks based audio track, and conformed to your session’s tempo. It doesn’t get much easier than this.

Workspace ET

For those of you who are used to working with REX loops, it should be noted that with the introduction of Elastic Time, the Processing Preference setting, Import REX Files as Region Groups is off by default. So, if you’ve recently updated to Pro Tools 7.4 and you’re wondering why when you drag in a REX file it no longer comes in as a region group, mystery solved. To return to your old way of working with REX loops, make sure that the Processing Preference for Import REX Files as Region Groups is checked, as well as the REX and Acid Files Only selection for Drag and Drop from Desktop Conforms to Session Tempo. From the Workspace, you can also audition REX loops at your session tempo when the Audio Files Conform to Session Tempo button is on. And, if when you drag a REX loop from the Workspace into the Edit window, you want the REX loop to automatically conform to your session’s tempo, again, the Audio Files Conform to Session Tempo button must be enabled.

REX Import Preferences

Copycat Cool

Apr 15 2008

There’s a saying, “Copying is the highest form of flattery.” Copying is also one of the best ways to hone your production skills. Taking the time to pick apart and recreate a song done by your favorite producer is almost like being an intern for that producer. You’re getting the benefit of dissecting the techniques used to produce their unique sound without the hazards of being an actual intern (you’ll never be shackled to the coffee maker nor asked to clean up after the band).

When selecting a song to copy, make sure that it is full bandwidth audio (like what you find on an audio CD), not a compressed audio file format (such as MP3 or AAC). You need to be able to hear every nuance of the original production, and a 128 kbps MP3 file just isn’t going to cut the mustard, there’s just too much audio content missing. You can audition MP3 files to find the song that you want to copy, but when you’ve identified the song, you should buy the audio CD to ensure that you’re listening to the best quality audio available.

The object of copying a song is to get as close to the original sound as possible. However, even though this is a great bar to shoot for, it’s not usually possible from a technical standpoint. For example, the producer used a $20,000 Lexicon 960L reverb unit, and all you have to work with is D-Verb (the Pro Tools LE factory reverb plug-in). Obviously, their sound isn’t going to compare. Fortunately, simply going through the process of copying the song as closely as you can is practice enough. Even if your copy isn’t a dead ringer, you’ll still be going through the steps and experiencing the techniques required to create the producer’s sound. Of course, ultimately, the idea isn’t to become a clone of your favorite producer, it’s to learn a variety of techniques and then to apply them in your own unique ways.

Neither is it necessary to copy an entire song, from start to finish. It’s fine to copy just a short section of the song. For example, the chorus, the bridge, or simply the intro beat. The production elements that you’re wanting to emulate are, more often than not, contained in only a few bars of the music. Copying just a section makes it convenient to loop the part, then beat match your session’s tempo to the loop. This also makes comparing your copy to the original song, right in your session, a total snap. Plus, with your session beat matched to the original, it becomes possible to extract the loop’s groove (using a tool like Beat Detective in Pro Tools) and apply it to your own tracks.

Here are some of the questions you should ask yourself when you copy a production:

copycat questions

Attached is a Pro Tools session in which I’ve imported and looped a short drum loop from Missy Elliott’s “Sockit2me” (produced by Timbaland). Then, I’ve used Xpand! and the Pro Tools LE stock plug-ins to copy the song’s basic production sound. It’s not perfect because of the limited palette of sounds I had to work with, but it certainly captures the flavor of the original beat. In fact, I even picked up an interesting production trick along the way: hard panning a gated reverb return to the left speaker, and then hard panning the original dry signal to the right speaker. See if you can hear this effect in the original loop and then find how I recreated it in my mix.

Copycat Cool Pro Tools

During this season of gift giving and gear lust I would like to remind us all (myself included) that it’s not the gear that makes great music. You’re the one that writes, plays, and produces the music, not the equipment. In fact, I bet, if you put your mind to it, you could write a cool beat with a kazoo and some cardboard boxes, and nary an AC outlet in site. But, instead, you’ve embraced high-tech music gear as your recording instrument of choice.

Sure, quality recording products give you the tools to make excellent sounding recordings. Assuming, of course, that you have some basic knowledge of music and recording engineering. However, ultimately, it’s the quality of the song that matters the most, because no matter how well a bad song is produced, it’s still a bad song. By comparison, a well crafted song that is also well produced has the potential to be a hit.

So, when purchasing your next amazing high-tech music making gizmo, keep in mind that it will not be able to magically make your songs better. If you already own all the equipment to record your tracks (for example, a computer, DAW software, audio interface, MIDI controller, and quality studio monitors), and you imagine that this next piece of gear will make your productions that much better, think twice before you spend your hard earned cash. Sometimes, it’s not a lack of gear that’s holding you back, but a lack of knowledge about how to use the gear you already have to its absolute fullest potential.

Fortunately, there is today a wealth of resources available to help you improve your craft, on both technical and creative fronts. If you can play an instrument and have a decent grasp of music theory and notation, you’re ready to jump right into production classes (such as Pro Tools 101 and Producing Music with Reason). If you’re shaky on the fundamentals of music and have not mastered an instrument, than you should start at square one and study music theory and an instrument (such as Music Theory 101 and Berklee Keyboard Method). If you’re not currently in a position to take Berkleemusic online courses, to start you on your way, treat yourself to a couple of books from Berklee Press (such as Instant Bass and Producing in the Home Studio with Pro Tools).

Lots of enthusiasm for making music is excellent, and most certainly a necessary ingredient to being successful in this industry. However, along with all that enthusiasm you’ll also need to know which end of a microphone boom to sing into. (See the YouTube video below.)

Happy Holidays! Have a safe and musical New Year!

Of course, just because you don’t understand compression doesn’t mean that you’re mentally challenged. As a rule, the compressor, and how it controls a signal’s dynamics, is one of the more challenging processors to grasp. Learning how to effectively apply compression in your mix can take a significant amount of study time, patience, and good old fashioned experience.

Now, I could explain what each parameter of a compressor does and how it affects the signal. I could even give you some compression presets to get you started. But, this approach would be old hat and does nothing to help you actively hear compression and how each of its components work. You see, without the ability to hear in your mind how compression colors a signal, and to then know which parameters on a compressor to reach for in order to achieve your sound, you’re just fumbling blindly.

The skill necessary to properly operate a compressor is comparable to the ability you developed as a toddler to recognize and apply colors. You learned to visualize what color you wanted to apply to the flower in your coloring book, and you learned which color to reach for in your box of crayons to achieve your objective. The trick with compression, as with any type of processing or synthesis used in music production and sound design, is to know, instinctively, which parameters to reach for in order to create the sound you’re hearing in your head. It’s a deceptively simple process because it’s so easy to quantify, but as we all know from experience, it’s tough to put into practice.

With all this in mind, I’ve cooked up an interactive compression lesson to help you better hear compression, and learn to associate compression colors with specific compressor parameters. It’s a Reason song file full of MClass Compressors, with each Compressor adjusted slightly differently, but applied to the same snare drum signal. Each compressor’s label reflects its parameter change (such as “More Attack” or “Less Attack”), so that you can easily identify the Compressor’s parameter that you’re hearing, in relation to a base compression setting (the “Basic Compression” device). And, since a sound is rarely heard on its own, but, instead, always with accompaniment, I’ve included the rest of the drum mix as a stereo stem on Channel 12 of the mixer.

Here’s How You Work It
Press Play to start the drum pattern, then, to hear each compression setting, solo each snare drum signal on the mixer (Channels 1 to 10), one channel at a time. Leave the drum mix on Channel 12 in solo mode so that you can hear how the different compression settings make the snare “sit” in the drum mix.

Many of the changes to the snare drum’s sound are subtle and a challenge to hear, especially if you’re new to this sort of critical listening. Accurate monitors are also key in being able to hear the differences in the drum’s sound. So, if you’re not hearing the differences right out of the gate, not to worry, below is a description of what you’re listening for in each compression setting.

Channel 1: “No Compression”
This is the snare drum dry, with no compression processing.
Channel 2: “Basic Compression”
This is a decent snare drum compression setting. It is the starting point from which a single parameter is changed in the following Compressors. For example, on the “More Attack” Compressor, all the parameters are identical to the “Basic Compression” settings except the Attack parameter.
Channel 3: “Less Threshold”
Increasing the Threshold means that less of the incoming signal will be compressed. Another way of putting it is that the threshold at which the signal will begin being compressed is higher.
Channel 4: “More Threshold”
Decreasing the Threshold means that more of the incoming signal will be compressed. Another way of putting it is that the threshold at which the signal will begin being compressed is lower.
Channel 5: “Less Ratio”
There’s no easy way to explain the compression ratio. It’s math, there’s no getting around it. Ratio sets the amount of input signal necessary to cause a 1 dB increase in output signal. For example, with a ratio of 4:1, an 8 dB increase in input will produce a 2 dB increase in the output. So, less Ratio means that an increase in input signal will sound louder at the output, less compressed compared to the original “Basic Compression” setting.
Channel 6: “More Ratio”
With more compression ratio applied, more input signal will be required to produce a 1 dB increase in output signal. Consequently, the output signal will sound more compressed when compared to the original “Basic Compression” setting. At high compression ratios, limiting occurs, where, at the most extreme settings, the output level stops increasing no matter how loud the input level becomes (referred to as “brickwall” limiting). In situations where the output level is very low in volume, you can use the Compressor’s Output Gain control to turn it up.
Channel 7: “Less Attack”
The Attack parameter sets how quickly the compression will begin. So, turning the Attack up means that less of the signal’s initial transient (the very beginning of its waveform) will be compressed. This is good if you want to retain the crack and pop of the waveform’s start.
Channel 8: “More Attack”
Turning the Attack down means that more of the signal’s initial transient will be compressed. This is good if you want to diminish the crack and pop of a waveform’s start.
Channel 9: “Less Release”
The Release parameter determines how long it will take for the compression effect to fade out. So, less Release equals a shorter release time and the signal’s waveform will be compressed for a very limited duration. This is good if you want to retain the natural decay of a waveform.
Channel 10: “More Release”
Turning the Release up means that the time it takes for the compression effect to fade out will be longer. This is good if you want to compress the natural decay of a waveform, like increasing the volume as the signal fades out.

After you’ve listened carefully to each compression setting, try describing the changes in the sound that you hear. This will connect what you’re hearing to a concrete idea in your mind. And, ultimately, help you to associate a compression color with a specific compression parameter. Once you master hearing what each compression parameter can do on its own, then you will begin to hear how all of the compression settings work together to create a variety of compression effects and sonic colorations.

Here’s the Reason song file. Remember to press Play before you begin soloing each snare drum signal, and only audition one snare signal at a time.

Compression Lesson (Reason 3 Song File)

Let’s Talk Reverb

Nov 02 2007

It’s true that with a Mac Pro computer you can probably insert a D-Verb reverb plug-in on practically every audio track in your Pro Tools session. However, this is a clear cut case of, “Just because you can do it doesn’t mean you should.” Reverb should be applied as a parallel effect, on a bus, in the send/aux return position. There are a few reason’s why:

1) The purpose behind reverb is to mimic the ambiance that’s captured during the recording of a live performance. With multitrack recording, performances are recorded at different times, often in different spaces, and sometimes with no ambience at all (as in the case of a direct line input recording or a virtual instrument). Consequently, there is an absence of the cohesive ambiance that naturally occurs in a live recording situation. Placing a reverb on your mixer’s bus let’s you send an appropriate amount of signal from each performance in your session through the same virtual space, just as if you had recorded everything live, in one space.

2) Reverb creates a sense of depth in your mix, of front to back space. The more reverb a signal is blended with, the further back in the mix it will sound. Alternately, the less reverb a signal is blended with the closer it will sound to the listener. By using a channel’s send to add different amounts of reverb to a performance you can bring an instrument forward, or push it to the back of your virtual sound stage. For example, a lead vocalist can be made to sound in front of the stage by mixing her with only a little reverb, while a cello can be made to sound at the far back of the stage by mixing it with much more reverb.

Always keep your reverb’s dry/wet mix parameter set to a 100% processed return. The reverb effect is created by mixing the dry channel signal with the wet reverb effect return. If your reverb’s dry/wet mix parameter is less than 100% you’re just returning dry signal back into your mix, and this is not the object. Use a channel’s send to adjust the amount of reverb you want mixed with a track. The higher the send level the more reverb effect return you’ll hear for that track.

3) Reverb, used correctly, on a mixer’s bus (in parallel), sounds superior in both clarity and depth than individual reverb plug-ins inserted on each mixer channel. When it comes down to it, that’s really what matters, it just sounds better.

In most modern DAW mixers you can send to a reverb in either mono or stereo. I prefer a mono send and a stereo return for most projects (such as dance, hip-hop, and alternative). However, a stereo send and a stereo return is equally acceptable and I often use this configuration when I want to achieve a higher degree of separation and fidelity (for example, a sparse acoustic recording or string quartet). Pictured below is a mono send/stereo return reverb configuration for Pro Tools (notice my choice of the “mono/stereo” version of the D-Verb reverb plug-in). I’m also attaching a Zip of a Pro Tools 7.3 session so you can dig around and see first-hand how it’s all set up.

Reverb 4 U Pro Tools Session File

Reverb 4 U