WAVESHAPE -- waveshape distortion synthesis
in RTcmix/insts/std

quick syntax:
WAVESHAPE(outsk, dur, freq (Hz/oct.pc), indexmin, indexmax, amp[, pan, wavetable, transferfunction, indexenv, ampnormalize {default: 1}])


4.0 Newer Documentation (taken from the source code):
older docs and more explanation below 
   WAVESHAPE -- waveshaping synthesis instrument
 
   p0 = start time
   p1 = duration
   p2 = frequency (Hz or oct.pc)
   p3 = minimum distortion index
   p4 = maximum distortion index
   p5 = amp *
   p6 = pan (in percent-to-left form: 0-1) [optional; default is 0]
   p7 = reference to oscillator waveform table [optional; if missing,
        must use gen 2] **
   p8 = reference to waveshaping tranfer function table [optional; if missing,
        must use gen 3] ***
   p9 = index guide [optional; if missing, must use gen 4] ****
   p10 = amp normalization [optional; default is on (1)]

   p2 (freq), p3 (min index), p4 (max index), p5 (amp), p6 (pan) and
   p9 (index) can receive dynamic updates from a table or real-time
   control source.

   NOTE: The amp normalization in this instrument can cause clicks at
   the beginning and ending of notes.  Passing zero for p10 turns it off.

   ----

   Notes about backward compatibility with pre-v4 scores:

   * If an old-style gen table 1 is present, its values will be multiplied
   by p5 (amplitude), even if the latter is dynamic.

   ** If p7 is missing, you must use an old-style gen table 2 for the
   oscillator waveform.

   *** If p8 is missing, you must use an old-style gen table 3 for the
   waveshaping transfer function.

   **** If p9 is missing, you must use an old-style gen table 4 for the
   distortion index curve.

                                                rev for v4, JGG, 7/22/04

Older Documentation:


WAVESHAPE


Waveshaping: a type of distortion synthesis wherein an input waveform is modified by a transfer function to produce an output signal. Thus, an input signal, x, puts out an output signal, y, by passing through a function defined as y = f(x). So:
   f(x) = x2 will exponentially expand the amplitude of the incoming waveform (Dodge and Jerse, 1985).

Other useful transfer functions to use are waveforms and Chebyshev polynomial equations, which can output pre-defined harmonic spectra.

WAVESHAPE(), the command in WAVESHAPE, uses makegen to define its transfer function. The makegen essentially draws a graph with input samples coming in on the x axis and output samples going out the y axis.

Syntax:


makegen(1, 24, 1000, t0, a0, t1, a1...) /* the amplitude of the output in time/amplitude pairs */
makegen(2, 10, 1000, p0, p1...) /* the incoming waveform defined by the relative amplitude of its partials */
makegen(3, 7, 1000, a0, g0, a1, g1...aN) /* transfer function for the waveshaper, where aN and aN+1 are amplitudes and gN is the number of points in the curve to interpolate between them (the sum of the g values cannot exceed the number allocated in p2, in this case 1000) */
makegen(4, 24, 1000, t0, a0, t1, a1...) /* the index envelope of the waveshaper, allowing the waveshaping to increase and decrease over time */

WAVESHAPE(outskip, duration, pitch, indexlow, indexhigh, amplitude, spread)

in comment form:

/* waveshaping instrument
*  p0 = start
*  p1 = duration
*  p2 = pitch (hz or oct.pc)
*  p3 = index low point
*  p4 = index high point
*  p5 = amp
*  p6 = stereo spread (0-1) 
*  function slot 1 is amp envelope
*     slot 2 is waveform to be shaped (generally sine)
*     slot 3 is the transfer function
*     slot 4 is the index envelope
*/

An example score:

rtsetparams(44100, 2)
load("WAVESHAPE")
makegen(1, 24, 1000, 0,0, 3.5,1, 7,0)
makegen(2, 10, 1000, 1)
makegen(3, 7, 1000, -0.7, 200, -0.5, 300, 0, 300, 0.5, 200, 0.7)
makegen(4, 24, 1000, 0,0, 3.5,1, 7,0)
WAVESHAPE(0, 7, 7.02, 0, 1, 10000)
WAVESHAPE(0, 7, 7.021, 0, 1, 10000)

Another score. Note that makegen 3 uses gen number 17, which creates a Chebyshev polynomial for defining harmonics:

rtsetparams(44100, 2)
load("WAVESHAPE")
makegen(1, 24, 1000, 0,0, 3.5,1, 7,0)
makegen(2, 10, 1000, 1)
makegen(3, 17, 1000, 0.9, 0.3, -0.2, 0.6, -0.7)
makegen(4, 24, 1000, 0,0, 3.5,1, 7,0)
WAVESHAPE(0, 7, 7.02, 0, 1, 9000, 0.99)
makegen(2, 24, 1000, 0,0, 1.5,1, 7,0)
makegen(4, 24, 1000, 0,1, 7,0)
WAVESHAPE(4, 7, 6.091, 0, 1, 10000, 0.01)