Huh... yeah? That reminds me of Monte Cook's old Bard Revamp in the 3e era. It was in "Book of Eldritch Might 2: Songs and Souls of Power".
Instead of having strict spells of different levels, you had notes, chords, and melodies. Notes could be cast as a move action, chords were standard actions, and melodies were full round action.
It also had a shifting use structure for their 'slots'. You could break down a chord into 5 notes, or a melody into 3 chords or 15 notes. Also worked in the inverse at the same rates.
The intention was to use multiple notes, or a chord and a note, in the same turn to be able to create songs of greater power than the individual note or chord. It also explicitly allowed multiple bards to contribute to the same song if they knew it, adding notes or chords to the overall melody.
It's just the name "Chords" that makes me think of it, but Monte Cook has always been a kind of inspirational "Take Risks" type of designer!
What's my deadline for bardsongs, there, Guy? Gotta have 'em ready for you!