I'm not sure how long Pandora Radio has had this feature, but now you can listen to music by genre.

Main genres include: alternative, blues, classical, country, dance, electronic, folk, hip hop, jazz, latin, new age, oldies, pop, r&b, reggae, and rock.

Each genre has sub-genres. For classical, sub-genres are: chamber (Baroque), choral (Baroque), opera (Classical), opera (Romantic), piano solo (Romantic), string ensemble, symphonic (Classical), symphonic (Romantic), and violin features.

Now, when I want something light, I have options. *Cheers*

Even better, it's free.