So the “three chords” thing (attributed to a punk zine from 1976) was useful for me to realize that anyone and everyone should be starting bands and making music however they can. Just get going already. You have everything you need right now. (Hell, Jonny Greenwood recently said that he didn’t know any chords when he first started playing with Radiohead. He literally had his keyboard turned off and no one else in the band noticed. He really took the advice about the importance of silence to heart, I guess.)
Once I’d absorbed that “just make music already” advice, this piece from Glenn Branca was massively influential for me to take things further. It provides the theory-informed intellectual underpinnings for why being “anti-theory” is a principled position to take if you’re trying to make truly “new” music:
The secrets of harmony are buried in a safe place beneath hundreds of years of music theory. Originally theory was called counterpoint and was invented solely as an instruction manual for rural choirmasters. It was cheaper than commissioning the likes of a Bach to give your town its own musical identity. Since theory was necessarily derived from an analysis of previously existing music, then any music based on that theory must itself sound like the music that the theory was derived from. In fact that was the whole point. Of course my point is that if you want to write something that doesn’t sound anything like anything you’ve ever heard before then this kind of self-referential theory can’t get you there.
The piece also contains a thoughtful refutation of the (dubious, imo) advice mentioned previously in this thread about (paraphrasing) how there are only 12 tones available in music, thus anything you could come up with has already been done, so don’t worry about trying to create something that sounds truly new:
Nicholas Slonimsky once wrote that it had been determined that there are 479,001,600
permutations of a single musical phrase based on the 12 tones of the chromatic scale. In that same light it can be shown that there are 4095 different chords that can be derived from those same 12 tones. But if one thinks in terms of chords that extend over the full orchestral range, using the 88 keys of the piano as reference, there are approximately
300,000,000,000,000,000,000,000,000 different chords that can be derived from those 88 tones. That’s 2 to the 88th power. Of course this calculation does not take into account microtonal intervals which would increase the size of the number astronomically considering that it is possible to get meaningful audible differences down to at least an eighth tone.
The point of such a demonstration, similar to what Slonimsky was trying to show, is that the
number of possible chords is inexhaustible. And of course with timbre and orchestration
introduced the potential is virtually infinite.
I don’t know how anyone else takes this information, but I’ve always found it profound and inspiring, sort of like learning about the vastness of our universe or how little of the world’s oceans we’ve truly explored (by some estimates, only 5%). So for the experimentally-minded, an addition to “go and make some music right now” might be “go and make some truly new music right now”. Nothing is stopping you, certainly not theory.