I had that same problem when I did Music App. The thing is that the kids doing that were in there just to get a credit. They didn't care about music, and there wasn't much I could do to change it. I don't know if your situation is similar or not, but that's been my experience.
What I did to try and break it up a bit for them was to do "Pop Music Friday." Where we did a song that they know, and we break it down a little, talking about the roots in the blues, and other 20th century influences. Then we listen to it, sing it, let them dance with it, and generally have a good time. My kids may not remember who Palestrina was, because we did go over all music from all over the world and from all time periods, but they left knowing the names of all four Beatles, why Metallica mattered, and why Beiber really was trash, but still important to popular music.
I didn't feel it was a complete waste.
I'm teaching music appreciation for the first time this year, and I've kind of been flying by the seat of my pants. We've done theory, composition, and an instrument unit. Now, we're starting on the Renaissance and... I'm absolutely lost on how to make this interesting to them. Everything so far has been interactive and hands on, I don't want them to just sit through lectures or videos on the Renaissance, I want them to do something! Does anyone have any ideas? How do you make music history appealing to bored high schoolers?
Also... I have four students in this class.