[sdiy] Generating acyclic waveforms?

[nicolas]

Based on your description of the physical goings-on it seems that perhaps a way to synthesize this analogically would be to start from an additive approach, with say four or more sine (would triangle be okay?) VCOs tuned to exactly 1F, 2F, 3F, 4F, etc.  Give each of those VCOs an EG/VCA or maybe even just mix them into a single EG/VCA.  So far a standard additive approach.  But then take either the 1F output after its VCA, or the overall mix output after its VCA, full wave rectify that and add it to the CV of the 2F, 3F and 4F VCOs (ie. feed it into a DC coupled FM input).  That would sharpen the harmonics in a way analogous to the increased tension from the fundamental vibration.  I don't think I have enough of a modular to do it, but perhaps someone who does could tell me how it sounds.

Cheers,
Nicolas


--- On Mon, 22/3/10, Veronica Merryfield <veronica.merryfield at shaw.ca> wrote:

> From: Veronica Merryfield <veronica.merryfield at shaw.ca>
> Subject: Re: [sdiy] Generating acyclic waveforms?
> To: "synth DIY" <synth-diy at dropmix.xs4all.nl>
> Received: Monday, 22 March, 2010, 12:42 PM
> The effect is called harmonic
> sharpening and happens in all materials used for
> instruments.
> 
> The process goes something like this. Imagine a taught
> string. It has length and tension. When plucked, it
> vibrates. Looking only at the fundamental, the string
> lengthens at the extremes of the excursion as does the
> tension. The next harmonic is therefore subject to higher
> tension and longer length. And so on. The amount of
> sharpening peaks at the note start and then decays away. The
> effect is the same in woodwind and brass but tends to be
> less so since the material moves a lot less than a string.
> However, it is this subtle effect that gives say a trumpet
> it's characteristic sound that a simple oscillator synth can
> not reproduce.
> 
> This is one of the reasons I started looking at additive
> synthesis and the Synergy. I have tried to do this in the
> analogue world with several sine VCOs but it wasn't easy.
> Each one had an envelope generator for pitch and amplitude.
> It is not as computationally expensive to do in software or
> FPGA as it might seem - a few adds and a couple of table
> look ups for each sine osc. The other thing to realise is
> that you only need a few harmonics to make the sound seem
> real. Many of the Synergy patches use 3 to 5 oscillators per
> voices to sound very realistic.
> 
> Adding noise to the reset level in a VCO is not going to
> modulate the harmonic content over the duration of a note to
> mimic harmonic sharpening.
> 
> Veronica, currently working on a Synergy based AU
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