Famitracker is a damn good choice. It's easily obtainable, has a good UI, covers a popular system, is simple enough to be SUPER effective in OHBs, and has lots of cool extension options (VRC6 for some extra channels, VRC7 for basic FM fun). It's my go-to for OHB.
The NES chip is also juuuust complicated enough to be interesting without being particularly tricky to learn.
That aside, Furnace is shaping up into a great jack-of-all-trades tool, so it's worth tinkering with a bit. LSDJ is great if you have an actual gameboy (or emu+controller in a pinch, but writing chip on the train is half the fun). There's a pretty steep learning curve to begin with but it becomes second nature surprisingly quickly.