I have had this clip from a remix or mashup of Cheryl Cole's Fight For This Love in my head for ages.

It is a loop of the "back" from "back to the start". Whilst that is looping a bassline then comes in over the top doing a 4 note decending pattern, possibly chromatic (or at least the first 3 notes). However I may have adapted it slightly in my head without realising.

It is really annoying me and I wondered if anyone knew the on i'm on about.