The Bartók string quartet cycle has been a career rite for quartets since the 1960s, and you can find any number of sets on the market by famed ensembles. There is quite a variety, from very sober, classical readings that emphasize the polyphony and take a very elevated tone (works well in the final String Quartet No. 6, on the dawn of war, where each movement is marked "Mesto," sad), to those that emphasize Bartók the folk music collector. France's Quatuor Diotima come up with often original readings that stand up to those of more famous groups. There are commonalities among the Bartók quartets, but Quatuor Diotima treat each one as an individual and play up the ways in which the composer responded to what was going on around him stylistically. The String Quartet No. 1 shows how Bartók emerged from an essentially French context, and the next three quartets get slashing, intense readings that derive from an Expressionist environment. Bartók's late return to Classical forms draws from Quatuor Diotima a Beethovenian tone. Sample the finale of the String Quartet No. 5, which is one of the most exciting readings out there. In general, you might disagree with a thing or two here, but "exciting" is a good general word. Naïve delivers ideal sound from the Deutschlandfunk Kammermusiksaal in Cologne.