As I remember it the "On the Road" passage is more about the audience's reaction to Shearing than about the performance itself.

There's a good one in Halldor Laxness's "The Fish can Sing", where two characters are trying out a piano reduction of a new composition they've never heard before (Roberto Gerhard's Violin Concerto). He gets the experience of something coming off the page and slowly beginning to make sense for the first time. (I still haven't managed to hear that concerto, but I've wanted to ever since reading Laxness's description).