People often ask me how my musical life affected my writing, and the answer is, in truth, they're practically the same. Writing every day feels very much like practicing music, which also has to be done every day. Building a character on the page is precisely like developing a character in an opera. Constructing plot is, for me, the hardest part of writing, and follows the same outlines as a symphony, with main themes, contrasting themes, creation and release of tension, climaxes, codas, and so forth. And probably the best thing about having been a musician, at least for the sort of fiction I write, is having developed an ear.
I always tell my writing students to read their work aloud, and I do it myself, especially in problematic passages. (Catch that? Another musical word.) Prose should have a rhythm that is both varied and appealing. It should be pared down to precisely the number of words needed to create the image, the affect (also a musical word), and impart the information necessary to move the scene forward or deepen the motivation. It should suit the narrative voice--sometimes strong and active, sometimes contemplative, sometimes poetic. I hope my students listen to their work, and begin to hear when a sentence or a phrase works, and when it doesn't.
Tangentially, and just to answer in advance another question I often get, I'm not a writer who can listen to music as I work. If I put music on that I like, I'm distracted by it. If there's music playing that I don't like--and oh, my, is there a lot of that in the world--then I'm irritated. When I listen to music, I listen to music.
Writing, for me, has been so much like singing. It's performance, and communication. And way too much fun.