Hi Phil – I was leaving this one for Italo. But, from the Ultrashifter documentation:
hysteresis: Controls how much the pitch may move outside the range of the current
note before the current note is changed to reflect that pitch. Hysteresis can prevent
the oscillating between adjacent notes that can occur when the pitch is in
between two notes. Notes are typically 100 to 200 cents apart so 50 cents of
hysteresis would allow
the pitch to wander a lot before a higher or lower note was
recognized.
range: Controls the smallest error in pitch that will be corrected – if the
pitch deviates from a true note by less than this amount, no correction will be
made. This value may be used to let vibrato through or to enable correction only
on notes that are badly out of tune