Well, consider the different types of instruments that are in this parade. You've got drums, maybe some trumpet and baritone players, maybe some flutists . . .
Here are a list of instruments and their sound effects (based on my own musical band class knowledge lol so they might not all be exact, plus my post is gonna look really silly with all these random text sound effects lol...):
Piccolo: TWEEE FWEEE
Flute: DOO DOO (and above if they're playing high)
Bass Drums: THUMP WUMP
High hat: RATATATATATA FRERERERE (rolled r's)
Baritone: WHONK WHONK
Trumpet: BWA BWA
Trombone: WAWHAAAAAAaaaaaaa (as it descends in tone)
That's just a few instruments off the top of my head lol So depending on the scene, put different sound effects together to really portray the sound of instruments. Don't pull all of them together in one scene because then it'll just portray a poorly played scene (in the reader's head, it'll sound like garbage lol). Maybe illustrate the woodwinds in one panel, and then the percussion in another, and then the brass in another).
And yep, music symbols too, but not too much. Illustrate the sound effects in a way that illustrates the instruments as well. Ex. a flute's sound effects will be very elegant and flowing, vs. a drum that will be very sudden and loud and explosive, vs. a baritone which is very low and mellow and dare I say it, overweight lol
Hope that helps! <3
