Feedback in FM synthesis

[Theo]

----- Original Message -----
From: Martin Czech <czech at Micronas.Com>
To: <WeAreAs1 at aol.com>
Cc: <synth-diy at node12b53.a2000.nl>
Sent: Monday, August 07, 2000 8:22 AM
Subject: Re: Feedback in FM synthesis


> But: Yamaha operators do PM, this sounds different.

Are you sure about this??
The programs I've used to simulate a DX all used FM and these simulations
worked accurate.
On the otherhand the Bhom modules (ICs disigned by yamaha) clamed to use PM.
The Bhom modules sound like DX (and can read DX patches dumped over sysex).
At the time it was argued that Yamaha wanted exlusive use of the name FM,
the PM thing was a invention of the marketing department.

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.
When using a vcf "sine vco" (self oscillation) for the carrier the results
are like FM.
Tuning remains a problem though.

Casio used PM or Phase distortion
Sounds quite different, like a cosine that is "pwm-ed".
Er... like when the first half from 0 to pi becomes "shorter" the second
half (pi to 2pi) becomes "longer".
The result is a waveform that moves from sine to saw.

Cheers Theo.