"The 4am is a mixtape file containing nothing but music donated directly by new and/or unsigned acts. The 4am is of no set length and is released on no set schedule. The 4am is mixed down to 128 of the kbps. The 4am is offended by the concept of sleep. The 4am is time’s combine harvester."

http://www.warrenellis.com/?p=5279

If you google 'warren ellis 4am' you get all the intros. That's pretty representative.