I could make a simple GUI with Tempo, Time Signature and number of count-in bars and a start button or shortcut key to start the count-in then it sends "spacebar" to the Biab window.
It could read the current tempo from Biab.
It I could do that in a few minutes someone should be able to add that into Biab ?

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BB-AHK-Metronome.mp4 (879.81 KB, 37 downloads)