Haydn's first ten quartets are often referred to as "quartet divertimenti," because like the serenade of divertimento, they have an extra dance movement, giving them five movements instead of the more traditional four. Of course, since Haydn invented the string quartet in the first place, it's a little hard to talk about "traditional" anything, but the serenade concept does indeed seem to characterize these warm, sunny pieces that have retained their popularity for over two and a quarter centuries. As is always the case with invention in musical history, once Haydn the string quartet genie out of the bottle, everyone tried to get into the act, but these really are the first works of their kind. All revolutions should be so much fun! --David Hurwitz