This change makes the saw do most of the slices without interpolation.
It also uses a fixed frequency for the entire 64 sample buffer, rather
than trying to sweep it linearly (the impact on quality is inaudible).
The calculation of slices is done with actual freq relative to sample
rate, so it should be more robust to sample rate changes. And the
strategy to use is lifted up out of the inner loop.
The total number of slices computed is reduced on both the low and high
ends (from 64 to 36).
Lastly, there's a very clever trick: the slice boundary is placed so
that the interpolation zone falls evenly between notes in 12tet in 44.1
and 48 kHz sampling rates, so the interpolated path will be very
unlikely in practice.
Raph Levien
102484e439