Ohh boy... LSD and music. My specialty.
In my opinion, if you you really want to get the most creativity from a single dose of LSD, don't actually spend the trip writing music. Spend the trip *listening* to music. That way, you gain invaluable insight into the art, which you can use to create music later when you're sober.
Select some really high quality work - you want to expose yourself to the upper echelon of musical talent. So, if you're interested in classical music, then of course Bach or Mozart would be good starting points. Or, if you want to produce psychedelic electronic music, then you might want to select a Shpongle album. Etc.
The final step is to take about 100 micrograms of LSD, and play the music in silent darkness. Listening is an entire skill in itself. I find that, in order to really appreciate very intricate jazz or classical music, I must create a perfect inner stillness, or silence, so that every note can resonate clearly in my mind. I like to imagine that my mind is a perfectly empty, black space. Then, the music begins to "paint" images into that space, and becomes animated in my imagination.
The reason that this works for creativity, is that you must expose yourself to other good artwork before you can create your own, and LSD is one of the best ways to do it. Creating good music without spending lots of time carefully listening to other musicians is like trying to send a text message without a phone. It just doesn't work.
