Formed at Juilliard in 1976, the Emerson String Quartet were pioneering from the start. They were one of the first quartets to rotate violinists between the first and second parts, and in 2005 recorded Mendelssohn’s Octet using two sets of instruments and sophisticated engineering techniques. In addition to their busy performing schedule, the Emersons—who will disband at the end of the 2022-2023 season—have amassed a vast recorded catalog and received a host of awards for their efforts.    This 1988 collection of Bartók’s complete string quartets, which was named Record of the Year at the Gramophone Awards in 1989, is widely acknowledged as the classic modern recording of these seminal pieces. Plenty of composers owe a debt to Bartók for their influence—Ligeti, Britten, Elliott Carter, and Kurtág among them—and along with the cycles by Beethoven and Shostakovich, Bartók’s remain among the greatest sets of string quartets. The concertos you’ll hear here were inspired by everything from unrequited love (String Quartet No. 1) to the Fibonacci sequence (No. 4) to the impending Second World War (No. 6).