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Tempo BPM / msec

Controls: Sgram/PT Dialog >> Pitch-to-MIDI >> Tempo
Changes: TB=n, T=n
Macros: TempoBPM, msTempo

These two controls set the Pitch-to-MIDI tempo for the sounds selected by the Tempo Voice and Percussion buttons.

Note that the Tempo set by these controls works the opposite of conventional music notation, which has a tempo based on the interval of a whole note and divides that down for half, quarter, eighth, and faster notes. Here, however, Tempo sets the interval of the shortest note, and longer notes are multiples of that interval.

So a performance that would conventionally use whole, half, and quarter notes must use Tempo set to four times the conventional beats per minute to get the proper timing for quarter notes; longer notes are then formed by using sustain characters in the Velocity Pattern, or by use of Hold Beats to extend all notes of a voice.

The BPM (Beats Per Minute) and msec controls are just different ways to set the tempo; changing one causes the other to change to the equivalent value. Since there are 60000 msec per minute,

msec = 60000 / BPM

BPM = 60000 / msec

The controls have an apparent resolution of 1 msec, but the actual tempo beats only happen on trace updates, which are controlled by the Trace Update Interval in the X-Axis Dialog. The default value is 10 msec. Actual updates may happen less often under heavy processor loads, or when interrupted by mouse drags.

Note that Tempo only controls the MIDI note rate; the Pitch Track note rate, and hence the note display, proceeds at the Trace Update rate. For example, with Trace Update at 10 msec (equivalent to a Tempo of 6000 BPM) and Tempo at 600 BPM, only one-tenth of the tracked (and displayed) notes will be converted to MIDI notes.

The tempo clock maintains the specified average tempo, even if the beat-to-beat interval varies. For example, suppose trace updates are every 10 msec and Tempo is set to 187 msec (about 320 BPM). The beats are thus constrained to times divisible by 10, so the first 5 beats arrive at 190, 380, 570, 750, 940, and 1130 msec instead of 187, 374, 561, 748, 935, and 1122 msec. There is a jitter of up to 10 msec past the target beat time, but there is no cumulative error.

MIDI Changes Script:

Use TB=n to set the tempo to n BPM.

Use T=n to set the tempo to n msec.

Note that n may be any valid integer variable or expression, including current MIDI control values, random values, current computer keyboard states or mouse position, input or buffered notes, or oscillators.

The value for BPM will be limited to the range of 30 to 6000.

The value for msec will be limited to the range of 10 to 2000.

Macro Notes:

TempoBPM=300 sets Tempo to 300 BPM. Alternatively, msTempo=200 sets the equivalent 200 msec.

Either control may be incremented or decremented by one. TempoBPM=>1 increments BPM by one. msTempo=>-1 decrements msec by one.

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


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