MintaBOOM by za909 is a new, work-in-progress music player, which aims to make it possible to play sample-based music in games without having to completely suspend gameplay. The additional cost of an IRQ source in a cartridge has also been considered, and as a result, no complicated mapper hardware is needed to make use of the music player, as it runs using the DMC channel for its timing!

http://forums.nesdev.com/viewtopic.php?f=22&t=14520