Setting Tuning Options
Different note pitches correspond to different frequencies. Difference between pitches is usually held very accurately, otherwise the listener will hear a lot of dissonances. However, the base frequency of the music scale is floating.
WIDI assumes standard European scale where first octave "La" equals 440Hz. However, recordings exist that are up to one quarter tone higher or lower. There is no natural sense to think of more than quarter tone difference, because difference of more than quarter tone corresponds to another base tone and difference less than quarter tone.
WIDI allows to compensate for such difference by either manual selection of "detuning" or by detecting it automatically, this can be controlled with the Tuning tab of the Recognition Settings dialog. WIDI not only detects amount of detuning, but also checks if the detuning is the same during the whole recognized piece, it is referred as "tuning quality". Tuning amount and quality, if determined, are shown in the Composition Analysis dialog.
Try to autodetect Global Tuning setting controls whether an detuning detection attempt will be taken. If it is successful (tuning quality is at least at the level "poor"), calculated value will be taken by Note Detection algorithm for setting etalon scale frequencies.
Autodetect Global Tuning even if algorithm ignores it is applicable only to Advanced Sensors algorithm with Local Tuning turned on, because in this case Global Tuning is overridden with Local Tuning calculations and therefore does not affect recognition results.
Manual tuning value is used if tuning is not detected automatically or if automated detection failed.