Kieron Gillen 
Phonogram Vol. 1 Rue Britannia (Full Color Edition) [PDF ebook] 

Britannia is ten years dead. Phonomancer David Kohl hadn’t spared his old patron a thought for almost as long– at which point his mind starts to unravel. Can he discover what’s happened to the Mod-Goddess of Britpop while there’s still something of himself left? A dark modern-fantasy in a world where music is magic, where a song can save your life, or end it.