On 2/27/14 6:33 PM, Theo Verelst wrote:
Frequency modulation, which is what happens when the "to be synced with" signal changes from one frequency to another is theoretically not limited in bandwidth,
the issue is that, however you try to model it, the result of a hard-sync oscillator is still periodic, for a fixed frequency ratio, and quasi-periodic if that frequency ratio is swept. that periodic function has harmonics that go on forever and we only need the ones that are below 10 to 20 kHz.
so that gives accruacy (aliasing) problems when the change is fast.
the aliasing problem isn't essentially about accuracy, as a property of the sample values coming out. it is about harmonic overtones folding over to non-harmonic frequencies and sounding like digital dog excrement. so the issue is how to not do that. at least to some perceptual extent. and this can be mitigated by somehow smoothing the "flyback" on the edges. a "perfect" solution might have to be algorithmic or the use of a lot of wavetables (with a little bit of crossfading between them).
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