Halldor Laxness, "The Fish can Sing" (mysterious celebrity singer where it isn't clear for most of the book whether he can in fact sing or not) and "The Atom Station" (subplot involving a sorta-Tolstoyan-anarchist organist with an up-to-the-minute knowledge of contemporary European art music).

W.S. Merwin, "The Mays of Ventadorn" (troubadour music).

Gunter Grass, "The Tin Drum".

Alan Spence, "The Magic Flute".

David Lindsay, "The Haunted Woman" (mysterious viol music as the key to another world) and passing mentions of music (mostly Scriabin or in the Scriabin ethos) in "A Voyage to Arcturus".

Alan Warner, "The Sopranos" (gritty story about a school choir).

Iain Banks, "Espedair Street" (rise and fall of a major-league rock band).

John Wain, "Strike the Father Dead" (hero is a 1950s British jazz trumpeter).

Isn't Ishmael Reed's "The Freelance Pallbearers" about New Orleans musicians? I've read some of his books but not that one.