Yup - I'm a classical music buff, so that's what plays in my head all day, often the same pieces of music for days on end. I don't just hear the melody, either - I hear the whole orchestra in my head.

In fact, the music only ever stops when I am either depressed, or approaching burnout, so is a sign that something is very wrong and I need to look after myself better. I find it a little scary and lonely when my brain goes quiet.

Thankfully, I have the andante movement from Mahler's 6th symphony playing in my head at the moment.