What is the Ableton Note Length MIDI Effect
The Note Length MIDI effect can be used to change the duration of the incoming MIDI note messages. This can be used to make a MIDI part sound more rhythmically consistent or automate note durations creatively. It can also be used to trigger your MIDI instruments with Note Off messages instead of Note On messages.
The Note Length MIDI effect has two trigger modes, which you can toggle to Note On or Off. In Note On mode, only the timing controls are active: Mode, Length, and Gate. You can use the Mode toggle button to sync the durations to the song Master tempo. The Length knob selects the MIDI's base length notes that the effect will output, and the Gate modifies this base by the percentage you choose. For example, if Mode is set to Sync, Length set to 1/4, and Gate set to 50%, the Note Length effect will output eighth notes (half a quarter note).
In Note Off mode, this MIDI device will output MIDI note messages when you release your fingers from your MIDI keyboard. This will cause the notes to play through your MIDI instruments, and the length of the notes produced can be set using the timing controls below. You can also use three other controls in Note Off mode. The Release Velocity control determines the velocity of the output note (relative to the velocities of the notes you played on your controller), and Decay Time sets the length of time it will take for an incoming the length of the output MIDI note messages, according to the pitch of the notes you play on your controller, from low to high. Set positive or negative values here to invert the relationship of the pitch to note length.