After serving in the military, Siebel began playing folk clubs, eventually moving to Greenwich Village, where he found support in the coffeehouse circuit.
[3] An article in The New York Times on February 14, 1970, written by Mike Jahn, described Siebel as "a folk singer with a country and western bias ... a 32‐year‐old native of Buffalo and musically a product of the Greenwich Village folk scene" and said that he "sings in high nasal and hillbilly manner, rather like Bob Dylan's singing in his early days", referring to his songs as "uncomplicated country and folk songs, with occasional thoughts about such things as suburban living and raising children".
At The Bitter End, he played acoustic guitar and was backed by David Bromberg, Don Brooks, Jeff Gutcheon and Gary White[4] In 1969, Elektra Records became aware of a collection of songs Siebel made with David Bromberg and signed him to record Woodsmoke and Oranges (1970) and Jack-Knife Gypsy (1971).
[3] His songs were covered by, among others, Bromberg, Willy DeVille, Linda Ronstadt, Bonnie Raitt, Jerry Jeff Walker, Kate Wolf, Mary McCaslin, Emmylou Harris, Waylon Jennings, The Flying Burrito Brothers, Rick Roberts and Leo Kottke; but he remained mostly unknown to the larger public.
Siebel played McCabe's Guitar Shop in 1978, which was considered a comeback, and appeared on a 1977 release, Music From Mud Acres, with a cover of the Hank Williams song "Weary Blues".