Music is another interesting crossover. The physical manifestation of music is material insofar as it moves air molecules in waves which is perceived as sound. But the music exist on the score as well and can be read and imagined by the mind.
Now you say well the score is paper and the ink is physical, but the music exist as a non physical idea like mathematics. The sounds not being necessary for the music to be heard.
"You were not there for the beginning. You will not be there for the end. Your knowledge of what is going on can only be superficial and relative" William S. Burroughs