[sdiy] Linear FM

[Andre Majorel]

On 2001-12-22 08:55 +0000, Scott Gravenhorst wrote:

> I should also have mentioned in my post that I've
> already done some web research, but wasn't terribly
> satisfied with the depth of information that I found.  
> I'm looking for information that will lead me to what 
> I need to do some FM work.  For example, I'm thinking
> of doing some modularization of at least one of 
> my FatMan synths, but I don't know if I can do anything
> at all with sawtooth oscillators.  Sinewaves seemed
> mentioned more than not, but other waveforms are not
> necessarily discouraged.

Not an URL but

  Chowing, John and Bristow, David
  FM theory and applications
  Published by Yamaha Music Foundation
  1986
  ISBN 4-636-17482-8 COO73

It explains FM in the context of the DX7 but it may apply (in a
DX7, the frequency of the carrier is modulated between f0 + delta
and f0 - delta, is this what you call linear FM ?)

It covers the following topics :
- modulation index,
- simple FM (modulating a sine with a sine),
- trees (one carrier, multiple modulators),
- chains (a modulates b, b modulates c),
- feedback.

> Would I be able to at least do *some* experiments with
> saw, PWM and square?

Sure, why not ? Most DX7 type patches use some form of complex
FM.

> Is it futile to play with only 2 or 3 VCOs?

You can get nice bellish sounds with just two sines.

Please let me know if you find any links.

-- 
André Majorel <amajorel at teaser.fr>
http://www.teaser.fr/~amajorel/