[sdiy] Additive Synthesis - phase shifts important??

[Tom Wiltshire]

On 14 Jul 2008, at 09:10, Paul Perry wrote:

>
>
> On 14 Jul 2008, at 07:30, Florian E. Teply wrote:
>> Altering the phase of a harmonic can have a significant effect on the
>> peak amplitude of a waveform. This can be significant if you are
>> trying to normalise amplitudes between various waveforms in a synth -
>> it can help to move the phases about a bit.
>
> It's true that the peak amplitude may change - as will the overall  
> waveform
> - hence my comment about LFOs.
> But the total energy will remain constant. Think Fourier analysis.

Yes, although the peak amplitude might vary, the overall energy (the  
"loudness") doesn't change.
Keeping the peak amplitude as low as you can for a given set of  
harmonics  gives you the best waveform resolution if you've got  
limited sampling resolution - so shifting the phases about can help  
improve waveform quality.

> I expect you are correct about FM synthesis, that being a non-linear
> process.

*I'm* not correct about it; I just read a paper by someone else,  
that's all!
John A. Bate, "The Effect of Modulator Phase on Timbres in FM  
Synthesis", Computer Music Journal, Autumn 1990.

T.