Finale does a neat trick with this. I have no idea how they process the input but they allow the keyboardist to tap the rhythm with a foot on the pedal while playing. There is an initialization dialog where the player taps the pedal so the program can sense the event to track. After that, the player can even speed up or slow down during the performance and the program still correctly tracks the rhythm because it counts, say, four even taps per measure even if the taps aren't really even. All the associated notes, then, are possitioned within the measure based on their proximity to the taps. The player is able to select a time value that helps control quantization of the notes so that small errors in precision of rhythm are rounded to the nearest note value based on the selected value.

Finale has other, more complex, ways of converting MIDI input into a score but this one seems pretty straightforward. They have an even simpler mode in which the player holds a computer key to select the time value and a MIDI keyboard key to select the note. I found this to be really awkward in practice. Typing ABC into a text editor is faster for me than this second method although I've used the first method with some success even though I'm not a keyboard player.

      - Mark