Songs of the Dead by Brandon Sanderson

When Jack Solomon, a struggling musician who works in London's West End, is killed, he awakens to a new reality in which light and music are used to create magic and where living eras ofthe past sprawl beneath modern London, layer upon layer, all the way back to recorded history.Jack also soon discovers that many of those who reside in the stratums of London's past have grown angry with the present world, and that their anger is being channeled by a powerfulsociety of light-and-music-based magic wielders who can cross the realms between life and death, between the present and the past. A past where the dead are sowing revolution against the living, and all of history is at stake.Welcome to the Strata Wars.