Perhaps are a genre bending/forward thinking band of utmost complexity. They could best be described as math rock, and are just as influenced by prog, as they are by free form jazz.
Perhaps first album, "Volume 1", has one continuous song on the entire album, clocking in at 37:48. They play very complex time signatures throughout the song, but then end it with an orchestra. So, you think you have heard it all? Try this album out, and see why you could be wrong. Recommended!