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From: mohan@topaz.RUTGERS.EDU (Sunil Mohan)
Newsgroups: net.music.synth
Subject: Re: Stupid Question About FM
Message-ID: <3646@topaz.RUTGERS.EDU>
Date: Fri, 13-Sep-85 12:11:46 EDT
Article-I.D.: topaz.3646
Posted: Fri Sep 13 12:11:46 1985
Date-Received: Sun, 15-Sep-85 11:57:13 EDT
References: <817@mit-vax.UUCP>
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 51

> I can't take it anymore! I can't wait a year to take Bose's accoustics
> course to learn this. What, exactly *is* FM sound synthesis and why is
> it so great? Somebody out there must know! I expect that I am simply
> missing something obvious because I do know:

 An excellent reference would  be John Chowning's  article on  FM  for
music. This was  republished in the Computer Music  Journal (I  forget
the issue, but pre 1980 I think), and also in the book "Foundations Of
Computer Music", both published by MIT press. And you do not need Bose's
Accoustics course.

I think there are two main reasons why FM is "so great" (I  personally
am not too impressed, but then the kinds of sounds I need are not that
readily, or at least easily reproducible in FM):

- Something to do with its being digital allows it to produce nice 
  "clean"   and strident sounds,  which   can easily  ride over  other
  instruments, making it good for leads in pop/rock.

- The  ability  to specify   time-varying modulation  ratios allows  the
  overtones  structure  (timbre) of  a sound   to  vary over its  Volume
  Envelope, and   with note dynamics. This  is  a prime  requirement for
  duplicating natural accoustic timbres.

All FM instruments allow additive synthesis, which  is inherently more
flexible than subtractive  by allowing arbitrary  overtone structures.
Note that the voluble  proponent of additive  synthesis, Wendy Carlos,
uses individual oscillators for the  lower overtones, resorting to  FM
only at the upper reaches.
This brings me to a burning question:
  
   Why do all Analog synths I have seen (inc the mighty MATRIX-12)
   have only one Voltage Controlled Resonance Frequency in their
   filter sections ?  Wouldn't having more than one add flexibility ?

Also FM allows  a greater variety of overtone   structures (as in  the
shape  of   the locus  of amplitudes of    overtones) than traditional
subtractive synthesis (see flame above).

Has anyone experimented with any of the following:
-	More than one VCF on a voice ?
-	Adding VCFs to a DX7 or sthg similar ?
-	Using a choruser/whatever on a DX7 to try to get "thick
	  analog" sounds ?
-- 

_
Sunil

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