Is this because playing sax is the only function he cared about preserving? Or did he perform other tasks too when they were operating in other parts of the brain?
> "To play an instrument means that you can understand music, which is a high cognitive function. It means you can interact with the instrument, you can coordinate both hands, you can exercise memory, you can count — because music is mathematics — you can test vision because the patient has to see the instrument, and you can test the way the patient interacts with the rest of the team," he said.
I take that to mean that playing the instrument uses many brain functions and so they're able to monitor many things at once.
Source: I'm an amateur musician. Judging that even I can play the instruments I know without needing to necessarily see the instrument or the notes to play (actually or imaginatively), I'd imagine actual professionals shouldn't have a problem.
Any practice routine worth its salt includes visualization exercises. For example, players are encouraged to use mirrors while they learn in order to strengthen their visual memory, and eventually players are taught to imagine the instrument in their head, to imagine practicing. This has shown to be a viable method for making real improvements while not even holding your instrument, including boosting your muscle memory as your body learns to make stronger associations.
[0] https://fundamentals-of-piano-practice.readthedocs.io/chapte...