Per Boysen

Don't bother please, I just found out: You have to press space bar first in Mainstage to get its AU plug-in sync clock going. I have to do this with the iDrume volume down though and then fade in the iDrum after Mainstage has hooked up to the external MIDI Clock input. Working fine now!

Hello guys, Does someone know the trick to make iDrum (or any host synced step sequencer plug-in) start with Mainistage when Mainstage is sync slave by external MIDI Clock? Mainstage is syncing fine, snagging the tempo right away. But iDrum plug-in set to "sync to host" doesn't start with Mainstage as it does with other hosts.

Mainstage uses the same patch library as Logic, regarding plug-in settings and channel strip settings. So you can look into buying any third-party library for Logic to use in Mainstage.