Ya know - I love and revere Giant Steps as much as the next guy - but your 'none of the classic rock titans' phrase just isn't true. I think John Lennon writing 'I am the walrus' to stump a university professor at music theory or Pink Floyd's musical choices on Dark Side, or Tom Scholz's understanding of scooping frequency bins when overlaying guitar parts on More Than A Feeling moved the needle as much as Coltrane modulating thru the circle of fifths, Mozart pulling 12-tone musik out of his arse 120 years ahead of Schonberg or anything John Cage ever did. Don't sell those guys short.
The 'What makes this song great' series on YouTube is fantastic if you guys are interested in the internal theory/arrangements of songs - Every time I start I'm up until 2am watching them all.
In the book that collects all the publicly available JOHN Lennon letters (great book for anyone interested) there is letter published in which Lennon responds to a letter he got from a Quarry Bank student in which he student asked Lennon what he meant in the words of his songs because they studied them at the school. John says something to the effect that whatever they meant to John at the time the listener was always free to interpret the song however he wished.
I think that letter from that student inspired Walrus. John said in an interview at some point it was written nonsensical to be impossible to interpret. I don’t think music theory played into it but that is just my interpretation of the facts as I understand them.
I am such a nerd. Sorry.