NSF or Nintendo Sound File format was designed several years ago by Kevin Horton. The NSF format resembles the SID or C-64 music file format, with Nintendo system particulars. The NSF format was designed so that anyone could extract code and data out of a NES ROM for use in a NSF player designed by a programmer.

Many players exist that are stand alone or as a plugin designed to be used with Winamp, a very popular music media player. I recommend using NotSoFatSo as the Winamp plugin of choice for playing NSFs. I recommend using GNSF, a stand alone player with several features that are also useful to those that wish to modify code and data of a selected NSF. I also recommend Slick NSF for NSF rippers. Slick NSF is also a stand alone player.

If you wish to learn how to extract NSF files from NES ROMs, I suggest that you view the links and material that I will provide below. There you will find links to various sites and a NSF document that I not only translated but also expanded to cover more methods, the document is not quite finished as of yet.