The Delay parameter in the Region inspector is mainly intended for creative musical purposes, such as rhythmically offsetting regions. It can also be used to fix timing problems in cases such as the following:
The attack phase of the sound is too slow. A good musician will automatically compensate for this by playing the notes slightly early. With very slow sounds, you may need a pre-delay of more than 100 ms to even them out.
The sound generator is reacting too slowly to the incoming note on messages. Older multi-timbral sound generators often take tens of milliseconds before outputting a voice.
The delay in output is not constant, as it is dependent on the order of notes arriving at the external MIDI sound generator. You should therefore try pre-delaying rhythmically important tracks by as little as one tick—it can work wonders on timing.
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