'[t[1]6502 machine code for the Nintendo Entertaiment System's 2a03 sound chip. NSF stands for Nintendo Sound Format.

A set of tools create .NSF files like '[[PPMCK], '[[NerdTracker] and '[[Famitracker].

NSF file format specs available from Kevin Horton at '[l[http://www.tripoint.org/kevtris/nes/nsf.html[CLICK HERE]