Using Multiple Outputs in Virtual Instruments

Get more instrument sounds out of a single software synthesizer

By Craig Anderton

If you think “multiple outs” means getting a double play in baseball, you’re in the wrong place! When applied to virtual instruments, multiple outs lets you separate different sounds within a multitimbral instrument, then send them to different outputs.

Multitimbral literally means “different timbres.” A multitimbral instrument can produce multiple sounds, with each sound typically responding to incoming data on a different MIDI channel. For example, you might set up a piano sound to respond to data on MIDI channel 1, bass on MIDI channel 2, lead synthesizers on MIDI channel 3, etc.

One of the first uses for multiple outs was drum machines. Sure, they had a stereo out for an overall mix—but generally, you didn’t want the same processing on, say, kick and tambourine. If a drum machine had four outs, you’d often assign kick to one, snare to another, and the rest of the kit to a stereo mix.

As hardware synths became multitimbral, multiple outs became more important because different instruments often demand different processing. Deep reverb on strings? Sure. On bass? Probably not. So, you’d assign different instruments to different outs, which went into different mixer channels. Each sound could have its own EQ, dynamics processing, special effects, etc. Clearly, this beat the “one size fits all” approach.

THE VIRTUAL LIFE

In the virtual world, here’s how multiple outs work. When inserting an instrument with multiple outs into a host like Sonar, you can create a separate audio track for each out (Fig. 1). Other DAWs work similarly.

Fig. 1: When inserting a soft synth into Sonar, you can choose a main output (shown here as First Synth Stereo Output) or all available synth audio outputs, in stereo or in mono (as shown here). The individual audio tracks work like any audio track—you can insert effects, mix, pan, automate, etc.

You can often have multiple outputs for instruments that are rewired into the host—but note there might be a lot of outputs, especially if you choose mono outputs. For example, rewire in Propellerhead’s Reason, and your DAW will sprout another 126 mono tracks. As a result, many programs give you the option to either create a track for every available output (which may be stereo or mono), or simply a single track—usually a stereo mix—for the main output.

Whether you should choose mono or stereo outputs depends on the instrument. XLN’s Addictive Drums (Fig. 2) puts some drums on separate channels of a stereo pair—for example, the kick is in a stereo track’s left channel and the snare is in the track’s right channel. If you insert stereo tracks for the outputs, you’ll be stuck with that particular placement. If you insert mono tracks, then the kick and snare will be on their own mono tracks, and you can pan them anywhere you want in the overall stereo mix.

Fig. 2: All of Addictive Drums’ outputs are shown in Sonar’s track view. Note that the drums are brought out to individual mono tracks, and that stereo tracks (like Overhead and Room mics) are also separated into left and right channels.

I WANT MORE...MORE...

Multitimbral synths or samplers can draw a significant amount of CPU power if you’re taking full advantage of the multitimbrality. To solve this problem, you can “freeze” tracks for instruments; for example, you could freeze instrument #1 before you start working with instrument #2. A DAW’s freeze function essentially converts the virtual instrument track into a more CPU-friendly hard disk audio track, then “disconnects” the instrument from the CPU. As long as you retain the MIDI track that drives the instrument, if you decide the frozen track needs further editing, you can always “thaw” it, edit the MIDI track, then re-freeze.

If you actually remove the instrument instead of freeze it, remember to note which patch you used and any other instrument-specific settings so you can reproduce the original sound if needed.

HANDLING EFFECTS

One big advantage of multiple outs—being able to add effects within the host—has been mitigated somewhat by instruments that include built-in effects. However, these are often optimized to keep CPU power consumption under control. For effects that want lots of CPU power and are intended to process several instrument sounds (like a good hall reverb), disable the instrument’s effects, and insert the reverb into a host aux bus. Then, use each track’s send control to apply some signal to the aux bus. In this case, the reverb is set for processed (wet) sound only, then brought back into the mix. Combining this processed reverb sound with the dry instrument sound will provide the desired amount of ambience.

MORE OPTIONS

Separate outs also have other creative uses:

• For simulated stereo imaging, load the same instrument into two programs. Restrict one instrument to a lower keyboard range (e.g., below middle C) and pan its output toward the left, then restrict the other to the upper keyboard range and pan its output more to the right. Lower notes will come out the left, and higher notes from the right.
• Setting two instruments to respond to the same MIDI channel can provide layering effects.
• Load the same instrument into two channels, but don’t restrict the key ranges; instead, tune one a few cents sharp, and the other a few cents flat. This can produce a huge stereo image, but check mono playback— you may need to edit the detuning to avoid “beating” or signal cancellation.
  

Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.