[sdiy] Imperfect VCO

[Czech Martin]

Reading out a sine table with a sine driven index is
exactly what happens in Yamaha-FM-Synthesis if a modulator
drives fixed and zero frequency carrier.

(voice from the off: oh no, he's going to ramble again why
FM is really PM...).

m.c.

-----Original Message-----
From: yasi perera [mailto:pi0say at hotmail.com]
Sent: Donnerstag, 31. Juli 2003 20:07
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Imperfect VCO


HI Everyone,

Hi Grant, you mentioned:
>Mike Firman wrote a C program that takes a harmonic
>input table, and generates a Mini-Wave transfer function that converts a
>unit amplitude sine wave into that harmonic series (Tchebychev method). 
>Just
>another static waveform, yawn.

I think driving wavetables with sines becomes a very interesting technique 
when one starts driving around in longer tables and modulating the amplitude 
and offset of the driving sine. it's neat that you mention it, as I was just 
thinking of a possible alternative to Tchebychev polynomials for generating 
these tables: cycloids. I'm not sure if it would work really, but I was just 
imagining: if I had a sine in my wavetable, and then read it out with a sine 
of the appripriate phase, wouldn't I get a cycloid out?
If that's actually true, then it seems to me that I could use the math 
describing cycloids to figure out what might be nice wavetables to use. But: 
this doesn't give spectral information like Tchbychev does, just waveform. I 
thought maybe the two in conjunction could be interesting, though. maybe 
first tchbychev and then a cycloid based analysis/resynthesis. a bunch of 
ittereations could make interesting data for a SFTV table.

Something to ask about, I geuss.

I did a quick search on "Mike Firman" and the program you mention, but 
couldn't come up with anything. I've been looking for a program that does 
exactly that transformation, so any information would be welcome

TIA, yasi perera

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