The song that is always in my head

For some reason this is the song in my head at all times. I hadn't heard the actual song in years until today...which made the radio in my head louder. I work at a coffee shop in Milford often and they usually play indie hits and such, but this song came on around 2pm. I am happy to announce that my internal radio now has more words to work with so it's not just a loop of 'rain drops keep falling on my head and that doesn't mean my eyes will soon be turning red...' ...'because I'm freeeeeeee.' Good times. Good times. What's your song?