In October of 1940, a Count Basie small group of Freddie Green, Jo Jones, Walter Page, Lester Young, Buck Clayton and Basie rehearsed with guest soloists Benny Goodman (not present on this track) and Charlie Christian in NYC. The rehearsal was recorded but remained unissued until the 1970s. The five tracks that were recorded convey a sense of informality regarding arrangement preparation, yet an extremely high level of musical sympathy. The track titled “Ad Lib Blues” (not to be confused with the Verve recording of Young with the Oscar Peterson trio from 1952) slowly grows out of Christian’s first four measures of unaccompanied soloing on a C blues. Christian’s playing gains confidence with the entrance of the rhythm section; by the end of his solo, the song’s arrangement has been set. Clayton and Young both follow Christian’s lead, taking a pair of choruses each. After solos, Young establishes a repeating riff that is quickly grabbed by the ensemble, with the track fading out during a half-hearted attempt by Christian at setting up a new ensemble riff.
Each chorus features an unaccompanied four-bar break, allowing the soloist harmonic freedom to lead from the I chord into the IV chord in measure 5 whatever way they may choose. Each of Young’s solo breaks feature twisting and turning chromaticism that sounds incredibly advanced yet retains a beautiful sense of swing. The first solo break outlines a ornamented chromatic guide tone of E♮ ascending to A♮, before descending back down to E. The second break also features an ascending and descending chromatic pattern, this time focused around diminished triads (D, E♭, E, and F).