i-fi sound effects use
triangle waves as both carrier and modulator.  See generators.scm for many other FM-inspired synthesis
techniques, including J0(B sin x): "Bessel FM".
An elaborate multi-carrier FM instrument is the voice instrument written by Marc Le Brun,
used in "Colony" and other pieces:
</p>


<!-- CLM CASE
<pre class="indented">
(definstrument vox (beg end freq amp 
                    &amp;optional (indexes '(.005 .01 .02)) (formant-amps '(.86 .13 .01)))
  (let* ((car-os (make-oscil 0))
       