This Battery 3 prepared-guitar kit's pads are color-coded to match their effects plug-in routing.
Although John Cage was not the first person to alter the timbre of an acoustic instrument with foreign objects (nuts, bolts, rubber wedges, etc.), he was the composer who, in the mid-20th century, famously applied the technique to a grand piano and wrote music especially for it. The preparation turns the piano into a percussion instrument with some pitched sounds, along with a variety of rattles, thunks and twangs. In 2004, Big Fish Audio (bigfishaudio.com) released an authorized and meticulously sampled prepared-piano library for $99.95 (see Web Clip 1). You'll also find a prepared Fender Rhodes library ($19.99) at the Website of French sound designer Les Productions Zvon, lesproductionszvon.com.
With a little attention to detail, you can create your own reasonably authentic preparations of acoustic instruments using a multi-output drum sampler and a few well-chosen effects plug-ins. For my examples, I'll use a sampled guitar, Native Instruments' Battery 3 and five common effects.
The primary advantage of a multi-output drum sampler is that pads have individual output routings, letting you easily choose and change the effect applied to each pad. Pads typically have controls such as volume, pitch and filter envelopes that are useful for sculpting the sound before effects processing. But most sampled instruments don't come in drum sampler format so you'll probably need to start by capturing slices from a conventional sampler.
Because you're radically altering the original sound to create a percussion instrument, you don't need multiple velocity layers, and grabbing two or three octaves is usually enough. Load up a sampler with the instrument you want to process and create a MIDI clip of consecutive whole-notes for the pitches you want to capture — for example, a few octaves of the chromatic scale. Adjust the tempo until each sample plays for its full length and then render the MIDI clip to audio. Slice the audio file to separate the notes and then load the slices into your drum machine's pads. I started with a sampled guitar offering 33 notes (E1 to C4) and used Iced Audio AudioFinder (icedaudio.com) to slice it up.
Next, insert the drum machine on a DAW track and route several of the drum machine's auxiliary outputs to their own mixer channels or to other DAW audio tracks to let you apply effects plug-ins; the exact method depends on how your DAW handles multi-output virtual instruments. The effect (or effects chain) that gets applied to each note is determined by the drum-machine pad routing (see the figure above). Once you've developed a good set of preparation effects, you can get added mileage out of them by re-routing your drum pads, and output routings are usually saved as part of the drum kit.
Plunk and Twang
For my prepared guitar I used five common effects: resonator, moving comb filters, granular processing, distortion and a physical-modeled pipe effect. I avoided obviously electronic sounds and effects with a tail such as reverb and delay because they're not true to the spirit of acoustic preparations. I used Battery 3's main output for unprocessed notes. You'll hear all 33 notes in Web Clip 2 — the first note is unprocessed, and the next five illustrate each of the effects in the order listed.
One thing you'll notice in prepared pianos is that the preparations often damp the notes quickly. The effects mentioned don't do that, but shortening the decay (with no sustain) on the pad's volume envelope accomplishes the same thing. Applying a small amount of pitch bend with a short pitch envelope is another effective pre-effects trick. Use the pad's lowpass, bandpass or highpass filter to place the sound where you want it in the mix. Because all these adjustments affect individual pads, you can use them to vary preparations routed to the same effect.
Using separate MIDI clips for the notes feeding each effect or for patterns of different length or meter is more flexible than using a single MIDI clip to play all the pads (see Web Clip 3). You might also sequence parts with the drum machine's built-in sequencer, or if it doesn't have one, with an external step sequencer.
Len Sasso is an associate editor of EM. For an earful, visit his Website,swiftkick.com.