The novella "Lucy Gayheart" by Willa Cather. The actress Joanne Woodward would re-read this book every year -- it was her dream to turn it into a film (which is a brilliant idea). She loves this book so much that years back she booked herself into Symphony Space two nights in a row and simply read the book aloud (and both nights sold out).
The reason why I think it would make a great musical -- it is set in the heartland (Haverford, Nebraska and Chicago, IL) at the turn of the 20th century. Lucy, the ingenue, is 21, a rehearsal pianist who plays for a famous opera singer, a baritone named Clement Sebastian, who is 49. Harry Gordon, 26, a banker, loves Lucy and assumes they will eventually marry, but she starts falling in love with Clement. There is also Lucy's older sister, a plain spinster who is envious of Lucy, Sebastian's concert pianist, a sour young man who despises Lucy.
There's a singer I think would make a striking Sebastian -- William Michals, who was in the ensemble of "Bright Star," but really stepped out when he was the standby for Emile DeBecque in Lincoln Center's "South Pacific." He's the perfect age range, perfect looks, and voice (baritone) to play Clement Sebastian.
If this intrigues you, you can download a kindle version of Lucy Gayheart right now. I could also send you an outline of the book (contains spoilers) to see why it could make a wonderful musical -- and eventually film.
Joanne W told me she is too old now to direct, so she's given up that dream -- but someone should pick this dream up and run with it.
Think about Joanne Woodward -- what a first rate actress she's been her whole career. This is her favorite book. Google Mel Gussow with her name and New York Times and read for yourself what she always wanted to do. Someone should do this. Maybe you?