Merrill played an important role in American popular music, tapping out many of the hit parade songs of the 1950s on a toy xylophone,[4] including "(How Much Is) That Doggie in the Window?

[6][7] Merrill was born in Atlantic City, New Jersey, and raised in Philadelphia over his family's candy factory and soda fountain.

His plans for a career in show business were cut short by the advent of World War II, when he was drafted into the Horse Cavalry Division of the Army.

[10] He had theatrical success with the 1964 musical Funny Girl starring Barbra Streisand, which introduced the standards "People" and "Don't Rain on My Parade".

Merrill's other Broadway credits include Breakfast at Tiffany's (1966), Henry, Sweet Henry (1967), Sugar (1972) (reworked as Some Like It Hot for a 1992 production in London's West End starring Tommy Steele and a 2002-2003 United States national tour starring Tony Curtis as Osgood Fielding, Jr.), and The Red Shoes (1993).

[14] He provided lyrics to "Loss of Love", the theme song composed by Henry Mancini for the 1970 Italian drama film Sunflower.

[15] He wrote the book and lyrics for the musical Prettybelle (1971), starring Angela Lansbury and directed by Gower Champion, which closed in Boston during tryouts.

[19][20] Merrill's screenwriting credits include W. C. Fields and Me (1976),[21] and the television movies Portrait of a Showgirl (1982)[22] and The Animated Adventures of Tom Sawyer (1998).