[sdiy] Wave terrain synthesis (was Re: Generating acyclic waveforms?)

[Tom Wiltshire]

I find it very interesting that this technique makes similar sounds  
to FM, since in my mind it is more closely related to wavetable  
synthesis than either of the nonlinear techniques you mention  
(waveshaping and FM). I can completely imagine that it is difficult  
to control or predict what you'll get out. Experimentation is good,  
but sometimes you're aiming for something particular and it would be  
nice to be able to get closer.

Thanks very much for a practical report on this.

T.

On 24 Mar 2010, at 03:46, Scott Nordlund wrote:

>
>> Simon Brouwer wrote:
>>> I see two other ways:
>>> - using wavetables (very long ones)
>> I'd discounted wavetables just because they would have to be very  
>> long,
>> but memory is cheap, so why not.
>>
>> What about Wave Terrain synthesis? Is there an sdiy implementation
>> anywhere? Load up a 2-d matrix with a surface of choice and then read
>> linear subsections. Altering the start and end coordinates over  
>> time to
>> vary the output waveform.
>>
>> -Dave
>
> I've tried wave terrain synthesis in Pure Data.  It's neat to think  
> about,
> but the results I've gotten aren't drastically different from FM or
> waveshaping or similar things (you could kind of consider  
> waveshaping and
> FM to be subsets of wave terrain).  My implementation scanned a  
> surface
> (defined by an arbitrary equation, F(x,y)) with a sort of lissajous  
> figure
> that could be scaled, rotated, offset, etc.  To get something decent
> sounding, I limited the surface and modulation to continuous, bounded
> functions (lots of sin, cos, atan).  A surface with discontinuities or
> singularities isn't going to sound so great.
>
> Anyway, yes, there's plenty of room for inharmonics and animated and
> complex sounding things, and it's nice that any of the inputs can  
> be used
> with envelopes or slow or fast modulation or whatever, but there's  
> also
> a lot of unintuitive messing about to avoid sudden and "unmusical"  
> timbral
> changes, or just to generally come up with something interesting.
>
> The end result resembles something that might be more easily  
> obtained from
> FM/waveshaping with arbitrary waveforms.  In fact that might be a  
> better
> approach, because it's difficult to make an equation for an  
> interesting
> surface.
>
> I'm not saying it's not interesting or potentially rewarding, but  
> it's not
> the revelation that I'd hoped for.  Imagine FM with several added  
> layers
> of confusion and obfuscation and you won't be too far off.
>  		 	   		
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