A couple of people have asked me about this privately, so I thought I'd post
this for the archives. Seasoned synthesists please ignore.
How to Synthesize Drum Kit Sounds:
A tom or kick has 2 elements - crack and body. A snare adds a third element,
snare rattles.
Crack: VCO sine out to VCA in. EG to both VCA and VCO FM1. Set FM1 amount
very large, so that the EG sweeps the pitch several octaves. EG attack at
zero, sustain zero, decay and release very close to zero. Play with decay
time, FM1 amount, and VCO pitch until you get a knocking or cracking sound.
Basically you want to sweep the pitch across several octaves so fast that
you can't hear it as pitch anymore. Patch kbd CV to FM2, but turn it down so
that the pitch doesn't change a lot as you play up and down the kbd. This
piece of the patch takes 1 VCO, 1 EG, 1 VCA. If you have a spare EG, using
separate EGs for pitch and VCA allows better fine tuning. It takes fast
envelopes to be able to sweep a VCO fast enough to be able to "crack" -
fortunately for us, the MOTM-800s work fine.
Body: Same patch as Crack. Set decay and sustain to about .75 - 1 sec. Turn
FM1 amount down a lot, so that the tone falls off in pitch only about a
semitone or so. Adjust FM2 higher than for crack, so you can play up and
down the kbd to get kick and toms.
Rattles: White noise to VCA, EG to VCA, zero attack and sustain, decay and
release around .75 sec. If you have a filter you can use, tune the noise
with some resonance for more realism.
Mix these 3 elements to taste. I can set my MIDI/CV converter to fire the
gate for rattles only above a certain note, so I can get kick, toms, and
snare at the same time. I only have 2 VCAs, so I patch a ring modulator as a
third VCA, although I get some signal bleedthrough.
Cymbals can be simulated by resonant filtering white noise, also swept
phasing or flanging adds realism.
You can spend a lot of time tweaking everything, and finding which notes on
the kbd sound better than others. It's a lot of fun. It won't sound like a
set of Ludwigs, but you can easily do the analog drum machine thing.
Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.
daveb@...