I play guitar, but I'm not much of a guitarist or singer. I really like songwriting, not trying to be polished as a performer. So I intermittently look into the AI world to see whether it has tools I could use to generate a higher-quality song demo than I could do on my own.
I've been looking for something that could take a chord progression and style instructions and create a decent backing track for a singer to sing over.
But your saying "Very soon you'll also be able to generate proper variations of an uploaded or previously generated song (e.g., you could even sing into Voice Memos for a minute and upload that!)" is very intriguing. I mean, I can sing and play, it just isn't very professional. But if I could then have an AI take what I did and just... make it better... that would be kind of awesome.
In fact, I believe you could have a very big market among songwriters if you could do that. What I would love to see is this:
My guitar parts are typically not just strummed, but involve picking, sometimes fairly intricate. I'm just not that good at it. It would be fantastic to have an AI that would just take would I played and fix it so that it's more perfect.
And then to have a tool where I could say, "OK, now add a bass part," and "OK, now add drums" would be awesome.