>> A classic for starting is the NES sound chip (Ricoh 2A03). It only has 5 channels and is very straightforward to use.
Such a simple chip and yet it was capable of producing amazing music in the right hands. Tim Follin created some legendary game soundtracks with that chip:
The Follin brothers used straightforward methods but took them to the extreme. Arpeggios? Double them and make them use complex chords. Triangle channel? Use it both as bass and drums. Note attack? Use the octave to simulate guitar sound. Wrap all that in prog rock composition and you get a very unique entry in the chiptune landscape.
Such a simple chip and yet it was capable of producing amazing music in the right hands. Tim Follin created some legendary game soundtracks with that chip:
https://www.youtube.com/watch?v=DzTDAgG4EXk
https://www.youtube.com/watch?v=4_gObHt1uZA
https://www.youtube.com/watch?v=ZQlLl2j5THQ