AW: Nonlinear Oscillators?

[Haible Juergen]

	>Has anyone out there tried to construct a nonlinear oscillator?  By
	>"nonlinear" I mean an oscillator that behaves like the nonlinear
	>elements in a traditional musical instrument (like an overblown
reed, a
	>bowed string, etc.).  I would love to have a musical instrument
that
	>could jump octaves like a wind instrument (i.e. with the same sort
of
	>noisy transition, not just clean octave jumps), or generate chaotic
	>subharmonics like a Gyuto monk, or growl like a sax, or create
	>multiphonics like an oboe.
	>
	>Any ideas? 

The first ideas I have to offer have probably nothing to do with 
"nonlinear oscillators", but with the smooth octaves transition
you mentioned (overblow etc.)

Fist, there is the good old Sync. To some extend, it does just
this, a smooth waveform transistion without getting nonharmonic,
between several harmonics. Problem might be that it also has such
a distinct "sync" sound, that it must be considered as a separate
effect of its own. However, the other than the "normal" hard sync 
schemes can be refreshing here. Try the EMS sync as described
on Graham Hinton's Page, it sounds *very* interesting, especially
when applied on the sine waveform.

Second, wavetable synths can do a crossfade between octaves.
It was either the Wiard or the Modcan that has a module to do
this. The "overblow" effect is mentioned.

Third, you can do wonderful things in that domain with triangle 
waveshaping. We had some discussion of certain Serge modules
recently, and I have posted some applications of my IS that go
in the same direction. If you feed a triangle wave into a "zigzag"
courve (consisting of separate triangles functions) with varying
drive amplitudes, you get a very nice "overblow" effect.
Funny, but I have a special instrument in mind right now that might
be a new diy project of mine, and I wrote to Magnus about it earlier
this week. Here's an excerpt: 
====
There is one thing I have in mind as a future project (but it's in
a very early stage): 
I want to have one large knob to play "fretless" within a 1 octave
range (like an ordinary laboratory function generator).
Then I will have a second knob (or slider, or lever) to fade between
octaves, using a Scanner. The octaves themselves would be 
generated by waveshaping. This should be easy when I stick to
triangle waves. These triangele waves will then be formed to
complex waveforms at the output.
My intention is to get a control that is fine enough to hit notes
precisely (large knob, 1 octave range), and still be able to
change notes fast (maximum 270 degree turn for the note, and
a few millimeters on a slider for the octaves).
An alternative for choosing octaves would be a set of fast responding
buttons, but the continuous scanning might also give interesting
overblow effects.
What do you think ?
====

>Also, has anyone tried filter FM, with the modulating signal being the
>output of the filter that is run through a nonlinear element (full-wave
>rectifier, clipper, suboctave divider, etc.)?  Both the allpass-FM and
>filter-FM methods would allow any signal to be run through the circuit,
>not just an oscillator.  I wouldn't think that either of these methods
>would produce the octave-jumping effect I am after, but I could be very
>much wrong.  

I didn't get octave jumps, but the method is extremely rewarding,
nevertheless.
On my CS-50, I have the main audio output plugged into the
"external in" all the time, so the audio output is available for
all modulations that the LFO ("sub oscillator" in Yamaha speak)
could do. I use it regularly to modulate the filter, and also the VCA,
and it is great to create a complex attack phase on an otherwise
boring sound. For example, the "Flute" preset becomes a trumpet
sound that rivals the VL7 in expression (and leaves it far behind
in terms of warmth), just with a little VCA modulation from the audio
output.
Larger modulation depths cause chaotic sounds, but the interesting
region is just "close to the edge". BTW, though I never exactly
analyzed this behaviour, but if memory serves the external input
of the CS-50 is ac coupled and I have it set to mic level (the trimpot
is a little hard to move on mine), so ther is probably some linear and
nonlinear processing in the feedback loop.
Might be interesting to evaluate this further on the Modular.

JH.