Only in musicals and they rarely sing their way through the entire day. Besides, musicals are separated from the other genres because human beings find breaking into song as unusual. All the better reason to attempt it.
Imagine the spirit of a person who loves to sing. She’s typically not a professional but her voice is sweet. Does he or she sing to escape reality? Does she become the lyrics? What kind of heart has she?
All this is grist for a novel. Will the reader identify? You bet. Human nature in all its beautiful manifestations is easily understood.
I suppose a story about a professional singer would need the author to dig in, but I haven’t read these either nor have we grown up in this environment. For those who have been blessed to be part of a musical family, think about it. Even a short story or novella would be greatly appreciated.
If anybody knows of such a novel, please inform me, I'd like to read it.
Singin’ In The Rain, Gene Kelly, 1952
BTW, anybody ever dance with their vacuum cleaner or broom?