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Pitch Hysteresis

Controls: Sgram/PT Dialog >> Hysteresis
Macro: PitchHyst
Changes: RH=n

When Spectrogram Pitch Track is active along with the Steps option, the display shows the nearest exact note instead of the actual signal pitch. But when the signal pitch is near the boundary between two notes, the display (and the Pitch-to-MIDI converter) may alternate between the notes due to vibrato or small random variations.

The Hysteresis control makes the note determination process "sticky", so that once a note is found, the signal must stray farther than the specified Hysteresis amount (in semitones) from the normal note boundaries. For example, if you set 0.5 semitone, then a tone that is nearly a half-semitone sharp or flat will still be reported as perfectly tuned. Since this is the note number used for Pitch-to-MIDI, Hysteresis can help a performance stay in tune despite tracking or playing errors.

The maximum Hysteresis value is 31.9999 semitones. Values greater than 0.5 should be used with caution, since this can prevent an intended note step from being properly detected. You will need to insure that each note stops (an instant of silence) before the next note starts. However, this can be a useful method for ignoring vibrato.

The purpose of such a large Hysteresis range is for use with Note Bend during Pitch-to-MIDI performances. When Bend is active, an ongoing note may be varied in pitch ("bent") over a +/-24 note range. This is ideal for tracking instruments with continuously-variable pitch, like voice, whistling, or slide trombones.

Of course, this only makes sense when used to play MIDI Instruments that produce continuous tones, like bowed strings or wind instruments, and not percussive instruments like piano or guitar which rapidly decay after the note starts.

One special application for large Hysteresis values is in conjunction with the +/-Octaves control to make a "bat detector" ultrasonic monitor that translates high frequencies into the range of human hearing.

Note that the Hysteresis value is saved to and loaded from MIDI Setup (.DQM) files. Loading a new MIDI Setup may change this value.

Macro Notes:

PitchHyst=0.25 sets Hysteresis to 0.25 semitones. PitchHyst=>1 increments and PitchHyst=>-1 decrements the current setting by 1/65536, which is about .000015 semitones.

MIDI Changes Script:

Use RH=n to set Pitch Hysteresis to n cents (not semitones), where n can be any integer or valid Changes script expression. This may consist of MIDI control values (including RH), random values, current computer keyboard states or mouse position, input or buffered notes, oscillators, or User Variables.

Note that unlike the PitchHyst macro and the main control itself, RH uses cents instead of semitones, where 100 cents equals one semitone. Only integer cents are allowed. So, for example, RH=50 is equivalent to PitchHyst=0.5.

See also Pitch Track Toolbox - Overview, Spectrogram / Pitch Track Controls, Spectrogram / Pitch Track (Sgram/PT)


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