Actually, I'm curious about the same thing. I'd be very impressed if it was (especially since it's quite rare for me to run into new SNES games with other people's music in it... not counting the ones that rip the music straight out of the SNES games from the 1990s).
The composer creates a small piece of software called an "instrument patch" with instructions to make sound. Digitally recorded sounds called "sampled instruments" can also be used. Here, we see a composer making some J-pop. Musical pattern data is being entered into a simulated computer at a temperature of 64 degrees fahrenheit.
OH, those organ chords are nice, and this track is really classy! You'll find a way around that interpolation. I can still hear a little bit of the hi-hat, or artifacts from them. I think it sounds good as it is, though!