My $.02 worth:

I don't "indulge" before or during rehearsels and performances. After I get through loading up my assorted instruments and electronic stuff, then it's time for the ganja.

I'm paid to entertain the audience, and I take this as a sacred obligation.

I've composed music and/or song lyrics both "straight" and under the influence of various "trendy chemical amusements"...some turned out great, some sucked.

I find song-writing "stoned" is best done with a tape recorder.