I reckon CAN would be a great alternative. It has inbuilt support for message prioritization, so important stuff like timing sync messages could have higher priority. Also it's differential so long cable runs are not a problem and it has good noise immunity. Oh, and it's a bus so virtually unlimited devices on the same bus, in any topology.

Oh, and also I've always wanted to use my synths in the car!

It would be nice if the protocol of the future was wireless and could support the actual audio as well though, but all that adds extra complexity of course.