This Fractional Delay uses Kyma standard IIR Filters in Allpass mode
combined with a sample-accurate delay to implement a micro-delay.
There are several examples given using different orders of filters.
Higher order filters are more accurate but more expensive. The 3rd
order filter is the lowest order that works correctly - the 2nd order
filter hits a boundary condition when the fractional part of the delay
goes to 0.
Test the sound by pitch-bending notes higher & higher above middle-C
until you hear glitches (clicking) in the pitch bend.
Note that the integer part of the delay has smooth delay changes
turned off, yet the transitions are still smooth (no clicking)
until the accuracy of the allpass filter is exceeded. This allows
for arbitrarily fast change in delay time without glitching or
artifacts.
-- RobRayle - 29 Oct 2005