I'm sort of coming at it from the reverse - If what Suno does is an 'arrangement', then it's more like a cover song - which means the original composers have rights? Clearly I'm not stupid enough to actually spend money on this, but The original writers of music and lyrics do have rights as to saying no - and of course organisations such as Harry Fox will licence you to do a cover of a song. So replacing lyrics removes the original writer's ability to collect royalties, but often it's music AND lyrics assigned to two people, so they share the total. Composers take people to court for songs that steal their melodies and chord structures or even rhythms - so with Suno being so good at copying, before long somebody rich will hear a piece of music that is clearly an arrangement of their song and let the courts decide. Will it be Suno in court or the person that did it? This will happen at some point, just to set a precedent.
The trouble with my own example is that we never formalised our writing - we were young and having fun, but all 4 of us think we wrote the same things. I remember maybe a couple of tracks that I think I wrote, but they also credit me on songs I don't remember at all? It patently doesn't matter as the songs were pretty awful from memory, but it is just strange to hear a credit for a piece of new music of my old music I don't remember?
