/melody works well, although at lower levels you may have problems with it because of missed notes. Although, iirc, /melody now recognizes some missed notes and will attempt the song several times. At some point though, it will just stop after a certain number of failures. Still good practice to learn how to manually twist songs, in my opinion.
Anyway, the ingame command is /melody # # #, where # corresponds to your song gems.
So if you want to twist regen in spell gem 1, haste in spell gem 2, and slow in spell gem 3, the command would be /melody 1 2 3.