“I had a sense that a voice existed that needed expression, that there was a voice that wasn’t being voiced.”

As some of you know, I like to read plays. A gambling buddy of mine (horses only, we’re not degenerates) works for a theatre company in NY, so he sends me things, and I always look forward to the plays in that Best American series. I think reading nothing but dialogue makes for good dialogue in my books. Anybody’s books, for that matter.
There’s something about SS’s quote that attracted me and I think it’s the last part, ” . . . the voice that wasn’t being voiced.”
I remember working with a student who had an angry narrator (girl) and a spunky sidekick. The other details — standard issue parents, a high school, etc. don’t matter. The narrator was the problem. The voice. It didn’t take either of us long to discover that the most interesting person in the story wasn’t the rather whiney narrator, but the sidekick. Insouciant and funny, the book glowed every time she turned up. That was the voice that wasn’t being voiced.
I’ve told a lot of students who are mired in their novels to look to the side. Is there someone standing there just waiting for a chance to sing?