A descendant of the family of the poet Heinrich Heine, Hart worked as a translator of German while attending Columbia University. In 1918, when he was 23, he met Rodgers, then 16, and their partnership began. They wrote the Columbia University varsity show of 1920. Their first Broadway success was The Garrick Gaieties (1925), which includes the songs “Manhattan” and “Mountain Greenery.” It was followed by a series of increasingly sophisticated musical comedies, among which were A Connecticut Yankee (1927), The Boys From Syracuse (1938), and, perhaps their masterwork, Pal Joey (1940).

As Rodgers matured into a hard-working, hard-driving professional, Hart remained the gifted amateur. His aversion to sustained work, keeping appointments, and meeting deadlines lent credence to Rodgers' description of him as “a partner, a best friend—and a source of permanent irritation.” In time Hart became increasingly addicted to alcohol and less and less reliable. The last show that they wrote together was By Jupiter (1942), a year before Hart's death.

Their long list of successful songs includes “Here in My Arms” (1926), “My Heart Stood Still” (1927), “Lover” (1933), “Blue Moon” (1934; their only song not introduced in a stage or film production), “My Funny Valentine” (1937), “Falling in Love with Love” (1938), “I Didn't Know What Time It Was” (1939), and “Bewitched, Bothered, and Bewildered” (1940).