A good sized backpack would have advantages over something shaped, for fitting music books into , for example.
Music sheets in plastic page covers in a 3 ring binder , then cry out for a decent music stand that will support the folio.
I find my older A cases fit A drybag style backpack #I found at REI,[base an oval like 4x10 speaker] #thicker, better padded TKL type cases wont fit.
given the slim outline that case may fit #well ..
alternatives: #GI surplus duffle bags # # .. sailbags .. big LLBean totes?
Johnny B Goode autographed Gunny Sack?
writing about music
is like dancing,