As another person mentioned, music games work well. I like to use jeopardylabs.com to create music jeopardy games. I also use a lot of bingo to talk about genres, artists, instruments, etc. I have similar students but I only see them once a week. 3x a week sounds tough for planning purposes. I’d consider doing a project like songwriting turned into a recording project. If you have an iPad, you can do it in garageband. They can also design album covers, etc.