For Famicompo this year I made an arrangement of John Coltrane's Giant Steps. Part of the project for me was writing the NSF almost entirely in C. I have made the source code freely available; it might be a useful example for how to use CC65 for the NES.
YouTube: video
ROM: coltrane.nes
Source: coltrane_src.zip
YouTube: video
ROM: coltrane.nes
Source: coltrane_src.zip