Written 1999/07/30
"Daddy, what's velocity range?"
What is velocity range? A question a child might ask, but not a childish question.
Velocity is a form of MIDI data that measures the force with which the keyboard is hit, and represents this force with a number from 000 to 127 or 001 to 128, depending on the machine. Velocity range means that a certain waveform on a sampler or wavetable synth will only sound when velocity from the controlling keyboard falls within a specified range . For example, suppose a sinewave has a velocity range of 000-064. When the keys are hit hard with velocity values over 064 the sinewave will not sound, but when the keys are hit softly falling within the range, you will hear the wave.
Different voices or sample layers can occupy various velocity ranges, sounding separately or overlapping. Suppose now you also have a sawtooth that sounds only with velocities between 65 to 127. Depending on the force with which the keys are hit you will hear either a sine or a sawtooth. You can assign as many voices to as many ranges as your synth/sampler's architecture will allow.
Here's an example of how I applied this with a sampler to good effect. I cracked out my analog synth and setup a simple resonant sawtooth sound. Setting the low-pass filter cutoff quite low, I took a sample and looped it, then I set the velocity range from 000-015. After creating a new layer I repeated the process seven times, each time bringing up the filter cutoff a bit and assigning higher velocity ranges for the layers that didn't overlap the previous ones. I also disabled the effect of velocity on amplitude on all the layers, so that all the waveforms could be heard loud and clear at all velocities. When I was finished I had 8 layers, each containing a different looped waveform, and having these velocity ranges: 000-015, 016-031, 032-047, 048-063, 064-079, 080-095, 096-111, and 112-127. The result was a sampled instrument which produced resonant sawtooth waves with a cutoff point that seemed to increase with higher velocities. When played it has that "percolating" effect you hear in a lot of techno music, and sounds so sweet when you run it through delay!
I also used the procedure above for an istrument where the velocity triggered samples of an FM sound with different modulation indices instead of filter cutoff points.
Now that you've seen a few examples of how velocity ranges can be applied, you're free to imagine all sorts of velocity-sensitive instruments. And they don't have to be the memory-conserving, single-cycle loop-based sounds mentioned above. You can use more elaborate waveforms in your creation, be it purely synthetic or a realistic emulation, limited only by your sample RAM and/or polyphony.
