Feedback in FM synthesis

[Don Tillman]

   From: "Theo" <t.hogers at home.nl>
   Date: Mon, 7 Aug 2000 16:20:39 +0200

   From: Martin Czech <czech at Micronas.Com>
   Sent: Monday, August 07, 2000 8:22 AM
   > But: Yamaha operators do PM, this sounds different.

   Are you sure about this??

John Chowning's original patent is FM.  US patent 4,018,121:
http://www.patents.ibm.com/details?pn=US04018121__

But the DX-7 patent is clearly PM.  US patent 4,554,857:
http://www.patents.ibm.com/details?pn=US04554857__

I don't know why Yamaha choose to use PM instead of FM.  I would think
that FM would generally sound warmer.

   When patching a VCO module as carrier the result is usually unlike
   FM.  Not sure why this is, believe it is the inner working of the
   VCO that makes it behave different.

For an analog VCO to sound like a DX-7 you would need very accurate
tuning, linear frequency modulation, through-zero modulation, a sine
output... and lots of aliasing and lookup table noise.  :-)

  -- Don

-- 
Don Tillman
Palo Alto, California, USA
don at till.com
http://www.till.com