I think he's given a different sound to every girl he's worked with (for the most part)
Kelly Clarkson - Since U Been Gone...this pop/rock anthem shot him into stardom and made him known as an A list producer
Britney Spears - Too many to list but her most recent lead single HIAM with it's pop dubstep influences was pure

Ke$ha - Tik Tok was the beginning of a whole new genre with him at the helm
Katy Perry - TD is bubblegum pop at its finest
But overall, I think he stans most for Ke$ha cuz he basically shot her into fame but I think he has the most chemistry with Britney
