So far I've tried my HomePod with various types of music, and I would say that the sound is less immediately impressive with classical, although the clarity and quality is exceptional. It could be that fully capturing the sound of a symphony orchestra, for example, is really something that you need a couple of HomePods to do justice to.
I will be trying that this weekend, as I have several of these to set up and experiment with. At the moment I'm listening to the Beethoven Violin Concerto, Wolfgang Schneiderhan on violin, with Eugen Jochum conducting the Berlin Philharmonic Orchestra. a 1962 recording I have in my iTunes library (ripped from CD to Apple Lossless). The sound is excellent.