Fourier-Analysis and FM-synthesis

[Michael Zacherl - Bacher Systems EDV GmbH]

> From thierry.rochebois at ief-paris-sud.fr Thu May 30 13:52:34 1996

> This is the very principle of the Hammond organ!
> This method has been used in electric organs since 1906 (telharmonium).
> 
> A multiple VCO versions was developed in 1966 by James Beauchamp.> 

Have the VCOs been in phase? As far as I can recall the tonewheels in
an early Hammond produced phaselocked harmonics.

> I think that the best ANALOG synth of this kind is an RMI additive
> synthesizer (it was used by Jean Michel Jarre on his hit Oxygen 4, it
> was used for the chorus sound). The RMI also have a VCF...

Hmm ... I'm not sure but at least the Oscillatorsection of the RMI Keyboard
Computer was digital. Wasn't the digital stuff the thing which
made the RMI famous? Or was there another RMI?

> By now, additive synthesis is quite rare as it is too calculation intensive...
> But, new algorithms are being developed (FFT-1) by Xavier Rodet and
> would allow the creation of new additive (and addictive) synthesizers (Oberheim).
> 
> Kawai is also working on this concept (K5000).

To recreate natural sounds by additive synthesis requires an OSC-VCA<-ENV
combination per harmonic. The oscillator has to be very stable in frequency
_and_ phase (the same like for FM-synthesis) and the envelope has to be 
multipart (time/level) - the more steps the better. 

Of course to create things like a flute or so some VCOs/VCAs and ADSR Envelopes
will do but in most cases it's the most complicated way to achive a good
synthetic recreation of a natural sound ('ve to admit it's capable of creating
_very_ realistic and dynamic sounds - but that's something for the digital
domain.)

The most distinguishable (sp?) part of most natural sounds is the attack
phase (e.g. see Roland's D-50). I'd funnel the effort in combinig noise-sources,
filters, resonators, envelopes to get 'like-a-...' sound IMHO.

;-)
/mz

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Michael Zacherl                           Produkt Marketing
phone : +43 (1) 60 126-278          Bacher Systems EDV GmbH
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e-mail: mz at bacher.co.at                A-1101 Wien, Austria
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