[1] He co-wrote, with Howard Greenfield and others, several pop hits in the late 1950s and early 1960s, including "Just Between You and Me", "Everybody's Somebody's Fool", "My Heart Has a Mind of Its Own", "Venus in Blue Jeans" and "Run to Him".

In the mid 1950s, he started hanging around the Brill Building, the heart of "Tin Pan Alley" in New York City, and was introduced to lyricist Lee Cathy.

Keller began working with and developing a young writing staff that included Carole King, Gerry Goffin, Neil Sedaka, and Howard Greenfield.

[5] When Don Kirshner and Screen Gems launched The Monkees in 1966, Keller co-produced their first album, and co-wrote several of their songs including "Your Auntie Grizelda" and "Early Morning Blues and Greens", both written with Diane Hildebrand.

[6] In 1984 he moved to Nashville, Tennessee, where he wrote songs recorded by leading country stars including Ernest Tubb, Crystal Gayle, Eddy Arnold, Loretta Lynn and Reba McEntire.