[sdiy] DCO Question

[Richie Burnett]

> Bonus points if you crossfade between one table and another to avoid 
> abrupt jumps in harmonic content and...

Yes, you can't allow harmonics to be popping in and out of existence 
instantaneously.  Even inaudible harmonics that are above 20kHz will still 
make a perceptible clicking sound if they appear or disappear abruptly. 
Strange huh?  It's due to spectral broadening.

Crossfading between one waveform and another version with less harmonics as 
you move through the troublesome pitch range is one way to do it, but it 
doesn't have to be done this way...  If you work with block-based 
processing, you can also do the crossfade between waveforms over the 
duration of one audio block if that's easier.  Even harmonics that fade in 
or out over a relatively short duration of say 1ms will pop *much* less due 
to spectral broadening than if they appear or disappear instantly.  And I've 
found it easier in practice to do the crossfade over a fixed time period 
like an audio frame, than crossfading between two waveforms over a range of 
pitches.

I hope I explained that okay!?

-Richie,