NSFE
NSFE is a 4 character file name extension for a new Extended NSF format. This format was extended by Disch and initially for his NSF Winamp plugin called NotSo Fatso as an extension to the original NSF format invented by Kevin Horton. NSFE was also created to add additional functions to NSFs such as timers for songs, fade-out time, arrange songs in a playlist, labels per song, the person who ripped the NSF and several other features. Since NotSo Fatso supports nearly every feature of the NSF format including all expansion chips, NSFE quickly gained in popularity. In order to implement these additional features, the format is chunked based. Thus, it's not ideal or possible to implement on any type of Famicom/NES hardware or FPGA type system without extensive modification. While the NSFE format shines on modern PC emulation platforms.
Read more about this topic: NES Sound Format