School music class accommodations for SPD kid?

My 9 year old son has SPD and is functioning pretty well in grade 4, with a shared aide. He's on a behavioral IPP (not academic) as he's quite able in most subject areas. Music class continues to be a problem. I've tried to problem-solve with the music teacher more than once, and asked for help from the resource teacher, but he's still not participating and demonstrating achievement. (He uses some of his typical tools in music, mostly the capacity to LEAVE the environment for a sensory break, but it's not enough.) The environment is by its nature challenging, but surely there's something we can do? He's got two more years with this teacher...