Pianist John Lewis, 80, who masterminded the Modern Jazz Quartet, died on Thursday. The M.J.Q., as the quartet was known, started recording in 1952 with Lewis, vibraphonist Milt Jackson, bassist Percy Heath and drummer Kenny Clarke. The group remained largely unchanged through the decades. When Clarke moved to Paris in 1955, Connie Kay replaced him and the quartet continued until Kay’s death in 1994. Lewis, who taught at Harvard, also performed with such music giants as Charlie Parker, Lester Young and Ella Fitzgerald.