High Quality Content by WIKIPEDIA articles! NSF is the DOS 8.3 filename Filename extension of the audio file format originally designated as NESM (Nintendo Entertainment System Music) by the inventor Kevin Horton. This format was originally designed for playback in a custom hardware device named HardNES by the inventor. Over the years, the NSF format has been implemented for playback on many platforms via plugins, stand-alone players, emulators and also the NES PowerPak.