Layering real-world sounds with synthesized drum parts puts a new spin on your drum tracks. You probably already have usable sound effects on your hard drive, because most commercial samplers have at least a modest collection in their factory library. Beyond that, you'll find thousands of royalty-free sound effects online. Soundsnap.com is one of my favorite sources, and it's free. The recordings don't need to be pristine for layering over drums, so don't overlook cheap sampling CDs, and consider grabbing your own sounds with a portable recorder.
Collect and Save
Start by assembling a small Foley library of short percussive sounds divided into typical drum-sound categories: kicks, snares, toms, cymbals, percussion, and so on. You'll generally want to layer drum sounds with Foley sounds that have a similar volume contour and frequency range. If you layer a Foley sound that resembles a kick drum with the sound of your hi-hat, for example, you'll quickly fill up all the space in your drum track.
Industrial, household, military, transportation, and vocal sounds make excellent fodder, but you will often want to extract a small slice, such as the last shot in a volley of machine-gun fire (snare) or the first bounce of a plastic bottle on concrete (tom). A browsing tool like Audio Finder (icedaudio.com) is invaluable if you have a large sample library. That lets you quickly audition clips, make basic edits, and drag-and-drop slices to your library.
If your synthesized drum part is step sequenced, you'll need to export its step sequences as MIDI files. Many drum synths do that, including Sonic Charge Tonic (soniccharge.com), Apple Logic UltraBeat (apple.com), and Submersible DrumCore (submersiblemusic.com). All of those come with a large collection of patterns exportable as MIDI sequences. You'll also need a sampler to play the Foley sounds; drum-oriented samplers are handier for that but are by no means necessary.
FIG. 1: The same MIDI clip plays the synthesized drums (left) and sound effects for some of the pads (right).
Start by loading a kit in the drum synth. Export one of its sequenced patterns, or create your own and place it on the sampler track. For some of the drum synth sounds, select compatible Foley sounds and map them to the same notes in the sampler that they're mapped to in the drum synth. Next, solo the doubled voices one by one in both the drum synth and the sampler, start the sequence playing, and tweak the sampler's voice parameters (filter, level, pan, envelope, and so on) to make the sounds work together (see Fig. 1 and Web Clip 1). Don't tweak global parameters such as effects, because that will affect all sounds played by the sampler.
Once you've configured your Foley track, you can do several things to add interest. I frequently use a second sampler for short vocal sounds. I'll have some notes trigger sounds in both samplers, and others in only one. Many samplers let you group sounds and assign notes and controllers to choose among them. You can then sequence these notes and controllers, or you can play them live to alter your Foley tracks.
Try applying DSP effects to individual Foley sounds. Multitap delays, distortion, phasing, and granular effects all work well when used sparingly (see Web Clip 2). You can apply DSP effects inside your sampler or route the voices to a separate output for DSP processing in your DAW. If your sampler doesn't offer either possibility, spread the Foley parts over several sampler instances on different tracks.
Sidechain compression or gating of the drum track with one or more of the Foley parts will highlight the Foley part as well as add variety to the drums. With compression, peaks in the sidechain signal will reduce the level of the drum track. Use a high compression level, say, 20:1, and balance the sidechain-gain and the compression-threshold, -attack, and -release controls to get the ducking contour you want (see Web Clip 3). Gating has the opposite effect; the drum track will be heard during peaks in the sidechain signal (see Web Clip 4). Here too, the sidechain-gain and gate-threshold controls work in tandem to determine when the gate is opened. Use envelope parameters (attack, release, and hold) to shape the gate's contour.
Keep in mind that once you've created a sampler instrument to complement your drum kit, you can reuse it with other sequences. You can also change one or more sounds in the sampler instrument without repeating the whole process.
Len Sasso is an associate editor of EM. For an earful, visit his Web site atswiftkick.com.
EM tutorial on creating Foley sounds by Brian Smithers
EM tutorial on extracting sounds from speech clips by David Battino