[sdiy] [synth-diy] numerically controlled superoscillator without hard sync

[Tom Wiltshire]

On 10 Feb 2014, at 09:35, Roman Sowa <modular at go2.pl> wrote:

>>> 
>>> We also need to consider that constant number of samples leads to
>>> unnecessary massive amount of calculations and samples at higher end, and
>>> surely too low sample count at lower frequencies, which requires filtering
>>> down to very low frequencies. Audio would be very limited if we don't want
>>> to hear the sampling clock, and IMHO it's not a nice thing to hear on any
>>> sound.
>> 
>> Easily optimized away by use of mip-mapping.
> 
> If I understood you correctly, that is going back to the idea of constant sample rate, where timbre may suddenly change noticeably between 2 semitones.

You *could* do mip-mapping with a variable rate, and you don't have to have a sudden change of timbre. My own experiments with it suggest that cross-fading from one mip-mapped table to the next is far preferable to switching. But it all uses more instructions.
Nonetheless, there will be some timbre change, partly from the table storing different data (that's the point of mip-ampping, right?) and partly from the harmonic distortion falling in a different place. If that change is gradual, I guess it becomes a "feature" - we call it "mojo" not "sloppy engineering", remember?

T.