My basic idea is a world with a “string theory” where the strings are actual metaphysical musical strings that manifest magical effects when “plucked” a certain way.
Sympathetic resonant induction. The interaction of frequencies is the underlying principle of both string theory and music theory. Assign various “flavors” of string which resonate with different elements/colleges/domains, spells sung or played properly in tune manipulate the fabric of reality.
Develop a musical language, look into Solresol and Enochian for some inspiration. Include monasteries with gongs and singing bowls, church organs, choirs, anything like that. Religions lean heavy into “the Word”.
I would definitely involve the Tritone, a chord that was considered evil by the church
Check out the old Lucasarts game Loom. It’s an old-school graphical adventure where you interact with the world using music-based magic. It doesn’t go too deep into the actual mechanics, but it’s a great game.
The anime Takt op. Destiny is pretty aligned to this concept as well
Check out the Songs of Roshar in the Stormlight Archive by Brandon Sanderson. But I guess this is a loose fit as magic exists without sound in the universe.
