I always have a song inside my head....

I noticed something today, whilst listening to a song by a band called 'Million Dead' ...the lyric repeats "i always have a song inside my head" and it struck a chord with me...i really do always have a song inside my head, no matter where i am, what i'm doing, how i'm feeling i ALWAYS have a song inside my head! Is this normal? is it an obsession with music?
I think being a hopeful musician with earphones in my ears 24/7 (almost...and they aren't too loud either) that i've become accustomed to having music in my head...and that's probably why there's something in my head all the time for me to relate to. Currently Switchfoot are the band i'm listening to the most...i seem to be relating with their music more than anything which is a good thing.