Timehole
Idea for Timehole (the non-linear novel I'll never write): So there’s a classical pianist in the 2040s who refuses to go into a “time hole” to write music. Basically, there is a headband you can wear that shoots acoustical signals to trigger lucid-dream-like simulations (inspired by Morpheus), where you can experience an hour in a minute (extreme time dilation). So all these musicians go into time holes for hundreds of simulated years and became savant-like, routinely. This classical pianist, the protagonist, is the last analog musician. This is all background context.
Suddenly, there is a UAP phenomenon, something like a first-contact experience, but they send us angelic/bizarre music, and the human race interprets them as wanting a response. The UN General (or whoever is in charge) offers the protagonist the ability to write the species-defining song, if he’s willing to go into a timehole. The idea is, even though he’s not as good as the “timehole composers,” he is the last classically trained maestro, and so his brain is structured differently, and if he were to go into a time hole, he would produce something more profound than the average person who goes in.
So he caves and he does it, and it’s this weird music writing odyssey, and somehow he ascends to a level of music-making where he can be bend reality/time. The ultimate twist is that the UAP phenomenon wasn’t an alien species, it was the musician himself breaking through reality from his timehole from the future.