this already exists and i think you are mixing things up a bit too

what you are talking is basically AI tools intergrated in most modern video/photo editing softwares. for music this would be either Music production software (called a DAW) or plugins which can generate Audio channels. planet coaster 2 on the other hand is a complete videogames, nothing to do with the very specific types of software i mentioned before. dont think it make much sense for frontier to start learning to code music software

dont forget, the ai needs to take its infos from somwhere too. so if there isnt a complete music production software the ai cant use it also wont be able to "generate" anything. i think this would be the same as asking for a music software to have the ability of rendering videoclips. i hope my explanation was kinda understable

id suggest you search youtube for the best AI music tools. ive been using some myself for some months now as im part time music producer