nesdev.org

I have a fairly working NSF emulator written in Go. Tested on mac and linux. Doesn't have a lot a features, and has a poor lowpass and no highpass, but it works. Comes with megaman 3 to demo.

Some docs to get it running: http://godoc.org/github.com/mjibson/mog/codec/nsf
Code: https://github.com/mjibson/mog/tree/master/codec/nsf

After port audio is installed

$ go test github.com/mjibson/mog/codec/nsf

Doesn't yet support: DMC, bankswitching.

I do not see the support of expansion audio either.

I have not yet come across that in my research, so I wasn't even aware it was missing. Thanks for pointing it out.

Expansion audio isn't used in any game released in the Americas or Europe. So unless you need to cover NSFs of Japan-only games or homebrew NSFs composed by fans of Japan-only games, you can put it off for much later.

Expansions are very commonly used in NSFs being made today. A quick glance at the last Famicompo shows that about 40% of the original entries used an expansion, and I think it was even higher in previous years. At the Famitracker forums, I think most of the tunes posted use expansions, generally.

Do these Famitracker forum users test their NSFs on a Famicom, on a modded NES, or only on an emulator?

All of those things are done by various users.

Jrlepage is the only person who regularly plays expansion NSFs on hardware though, since he imported a TNS-HFC3 to do it: http://famitracker.com/forum/posts.php?id=3633

Many users have a PowerPak and a modded NES. Some of us have a Famicom as well.

Most users just use emulation.

Similar to anywhere else, really.