Resident Duke University chamber group, the Ciompi Quartet, continues its Lunchtime Classics series, with the second of four all-Mozart programs addressing his most significant work for quartets. The multifaceted composer's String Quartet No. 18 in A Major fills the 50-minute program, with a planned introduction by one of Ciompi's mainstays. In Ciompi's difficult-to-define wheelhouse of standard repertoire and modern commissions, this quartet sits on Haydn-inspired tradition, while stretching its four movements into rhythmic games and counterpointed themes. All Lunchtime Classics concerts start at noon and are free and open to the public. Audience members are encouraged to bring food. —Margaret Hair