Usually in the mid/low 70's as understandable conversation can take place while the music is playing.
However, when I have a migraine I sometimes listen @ much louder levels when laying down on the sofa with the lights out.
Being in bed/dark quiet room with a migraine is the stupidest advice I've yet received from experts in the field as a distraction works wonders/sans major pain killers.
My distraction is music, which is often Motzart and/or The Who's Quadrophenia.
DeKay