Midi Files
Nosefart is an NSF plug-in for Winamp. That means it plays NSF files.If you don't know what NSF files are, but you do know what C64 SID files are, just pretend they are the same thing, but for the NES. If you don't know what SID files are, then NSF files are the music code from NES games ripped right out of the game. All that's needed to accurately play the music tracks back are accurate 6502 and NES sound register emulation.
If you don't know what Winamp is, try http://www.winamp.com. They'll tell you.
Winamp nsf Plugin
Nsf Collection