Honestly, to me, it matters what genre and what exactly I'm listening to.
Usually I would blast Jazz, Classical Music, Hard Rock and Certain sub-genres of hip hop (Instrumental, Nu-Jazz, Trip-Hop,etc.) to look for different subtle and most of the time complex, (at normal volume) components that make up different parts of the song.
I never understood why people Blast alot of straight rap-music so long since there is usually not much complexity within the rap music itself. Save the fact of course that you cannot hear the music itself.