I’ve been trying to track down this short story I read some time ago, but have had no luck so far, so I’m hoping someone else might know it. I believe it was in an anthology, which I read sometime in the 2000’s.
The premise is that the protagonist shares the experience of his alternate selves in parallel universes. One plot point I remember is that he makes a living selling pop songs from other universes. He witnesses a murder or a kidnapping occurring, and tries to save the victim, who I think is a girl or young woman. While doing so many of his alternate selves dies, and in the end he saves girl but there’s only a few or one of him left.
I was going to suggest Paul Melko also, but a 2006 Asimov’s story called The Walls of the Universe, which appeared in his collection called Ten Sigmas (and was also the first section of a novel also called The Walls of the Universe.
I guess maybe he re-used some of the same ideas across different stories. iirc, his protagonist also tried to make money by importing pinball into a timeline where it didn’t exist! But that was probably in the novel, not the orignal short story.
The novel also had a sequel called The Broken Universe.
Yeah, I’ve read both those novels and Melko’s other novel (Singularity’s Ring) too - I’d like to see more from him. Your comparison with Steve Gould seems apt.