His fellow songwriters freely acknowledged that Johnny Mercer had the greatest range and versatility of them all. Where other lyricists, such as Oscar Hammerstein 2nd, established a long-term partnership with a single collaborator, Mercer wrote with virtually every great popular-song composer of his day. Because the music always came first, Mercer had to adjust his lyrics to his collaborator's musical idiom, from the lush melodies of Henry Mancini ("Moon River," 1961) and the folksy strains of Hoagy Carmichael ("Skylark," 1941) to the blues and jazz of Harold Arlen ("That Old Black Magic," 1942) and Duke Ellington and Billy Strayhorn ("Satin Doll," 1958). At the height of his career Mercer wrote with Jerome Kern, his boyhood idol. Near the end of Mercer's life Paul McCartney, who idolized him, wanted to collaborate with him.

Mercer was unique in being the only lyricist of his day who was also a successful singer, prefiguring such singer-songwriters...