quaintquant
I think the absolutionist take here is unproductive.
I would argue a writing a fugue is analogous to "building a computer program"; to say little of 12 tone chromatic atonal music compositions that usually sacrifice 7 tone based harmonies for interesting structure, like palindromic reflection of ascending and descending musical ideas, and optimising for a high number of pitches in a melody.
Additionally, 7 note diatonic music theory can be completely summed up with two statements:
1) tick-tick-tock-tick-tick-tick-tock
2) permuate all the things!
Most common western instruments are literally built to only play 7 tone diatonic music theory.
Look at a piano. It can literally ONLY play "semi-tones". It's impossible to explore music beyond the 12 note chromatic scale without first modifiying the physical construction of the piano.
Should provide a solid foundation, and plenty of insider jargon to follow up on!