I also listen to classical music on TuneIn. I hadn't come across KUSC before but have it playing now. The ones I use regularly are All Classical Portland, WQXR, WCPE and King FM Symphonic Channel (for that, you have to say "play K-I-N-G-F-M-S-D-3).
It is very hard to get specific tracks from Amazon Music, and the only way to get a symphony is to set up a playlist or ask for an album.