STKVoicForm — STKVoicForm is a four formant synthesis instrument.


STKVoicForm is a four formant synthesis instrument. This instrument contains an excitation singing wavetable (looping wave with random and periodic vibrato, smoothing on frequency, etc.), excitation noise, and four sweepable complex resonances. Measured formant data is included, and enough data is there to support either parallel or cascade synthesis. In the floating point case cascade synthesis is the most natural so that's what you'll find here.


asignal STKVoicForm ifrequency, iamplitude, [kc1, kv1[, kc2, kv2[, kc3, kv3[, kc4, kv4[, kc5, kv5]]]]]


ifrequency -- Frequency of note played, in Hertz.

iamplitude -- Amplitude of note played (range 0-1).


kc1, kv1, kc2, kv2, kc3, kv3, kc4, kv4, kc5, kv5, kc6, kv6, kc7, kv7, kc8, kv8 -- Up to 8 optional k-rate controller pairs for the STK opcodes. Each controller pair consists of a controller number (kc) followed by a controller value (kv). The 5 controller numbers and values that work for STKVoicForm are:

  • kc, kv -- 2, voiced/unvoiced mix.

  • kc, kv -- 4, vowel/phoneme selection.

  • kc, kv -- 11, speed of low-frequency oscillator.

  • kc, kv -- 1, depth of low-frequency oscillator.

  • kc, kv -- 128, loudness (spectral tilt).

[Note] Note

The code for this opcode is taken directly from the VoicForm class in the Synthesis Toolkit in C++ by Perry R. Cook and Gary P. Scavone. More on the STK classes can be found here:


Here is an example of the STKVoicForm opcode. It uses the file STKVoicForm.csd.

Example 761. Example of the STKVoicForm opcode.

; Select audio/midi flags here according to platform
-odac     ;;;RT audio out
;-iadc    ;;;uncomment -iadc if RT audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o STKVoicForm.wav -W ;;; for file output any platform

sr = 44100
ksmps = 32
nchnls = 2
0dbfs = 1

instr 1

ifrq	=	p4
ksel	line	p5, p3, p6				;Vowel/Phoneme Selection

asig	STKVoicForm cpspch(p4), 1, 2, 1, 4, ksel, 128, 100, 1, 10, 11, 100
asig	=	asig * .5				;too loud
	outs asig, asig


i 1 0 5  7.00 100 0
i 1 + 10 7.00 1  50


Author: Michael Gogins (after Perry Cook)
Irreducible Productions
New York, NY

New in Csound version 5.11