You can record wave files while playing NeoRAGEx, then convert them to mp3, & probably do other stuff with a sound edit program. I don't know, just stand there & don't shoot/do any actions that employ SFX.
You've already spent how much on NG stuff? You've likely already paid good money for the privelege of owning the NG + games, who cares if you use an EMU to make yourself a song, that for one thing is NOT AT ALL AVAILABLE on ANY commercially released or even pirated CD.
It's not going to kill you to fire up NRX and piece together an mp3. What you do with the emulator is your own business really.