Reportedly, Thelonious Monk never liked his compositions being recorded by other artists. However, there were exceptions and one was Steve Lacy's Reflections, the first all-Monk-composition album recorded by someone rather Mr. Monk himself. Recorded in 1958, it also featured with Mal Waldron, Buell Neidlinger and Elvin Jones.
Whether because of the release of that or Monk's personal liking for Lacy, Monk invited him to play along his quartet in 1960. Monk had already complimented Lacy in at least one occasion: during a gig at the UN building in New York City, Jimmy Giuffre Quartet featuring Steve Lacy played opposite Thelonious Monk where they performed two Monk's compositions. The composer almost instantly hated it, however he had some nice words in his sleeve for Lacy and right after that UN gig he invited Lacy to play with him in the Jazz Gallery. Other gigs followed in 1960.