NSF is the sound file format for the Ricoh 2A03 chip used in the Nintendo NES/Famicom game console. The nsf filetype also supports additional sound expansion chips.
At BotB, expansions are only allowed in the "nsf plus" format. The nsf format is for 2A03 ONLY.
The 2A03 has five sound channels: two pulse waves, one triangle, one noise, and one DPCM channel.