[rchaud]

That's called 'jamming' and it's been possible for musicians since the time cavemen figured out they could hit sticks on things to create a rhythm.

[ndriscoll]

If the computer is fast enough to keep up with real time music, one could imagine a model that can jam with you with other instruments, reacting to and complementing what you're doing.

[deadfoxygrandpa]

thats basically existed at least since 1990 with band in a box