While at MIT, Lagin also completed jazz coursework at the Berklee School of Music. He was deeply influenced by the jazz world in New York City, particularly pianist Bill Evans, who he met in Boston and saw perform many times in New York and Boston in the late 1960s and early 1970s. During this period, Evans wrote out some of his tunes for Lagin. His piano teachers included Dean Earl, a Charlie Parker sideman, and he studied jazz improvisation with Lee Konitz. He played piano in the MIT Concert Jazz Band and MIT Jazz Quintet led by Herb Pomeroy, a sideman with Duke Ellington and Stan Getz.