Most gates have a KEY input. Have your midi playing audio and route the audio to the key input of the gate. I have used this to create in time tremolo fx on GTR tracks by routing the klik to the key input and it works great. If you have enuf trax you can also use this trick to open tom gates BEFORE the sound by copying your audio track, moving it earlier in time and using it as the key for the original tracks gate. Good Luck, Dave

Another old trick for gating is to use the kick drum to open a bass track gate. Some times you have to take attack out of the bass track being gated, but it works to tighten up the rythm section. But as far as I know you have to use audio to trigger gates.