Mulligan and Monk had gelled when they'd met previously in various impromptu playing situations, this giving Riverside producer Orrin Keepnews the idea that they might record together successfully. It was decided to use Monk's own rhythm team and mostly his compositions aside from ‘Sweet and Lovely’, and a version of ‘Undecided’ re-fashioned by Mulligan as ‘Decidedly’. Originally it had been proposed that a larger ensemble would be used on some tracks, but this idea was abandoned once it became clear that the co-leaders were content with the quartet format.

‘Round Midnight’ is a tad tentative at first, each man feeling the other out. Mulligan plays the tune, Monk's comping quite asymmetrical; then gradually Mulligan is emboldened to build his solo as he wants, the effect suitably lyrical, Monk's own solo like a compendium of his keyboard quirks, bass and drums quiescent. ‘Rhythm-A-Ning’ then goes at quite a lick, Wilson in zippy form as Mulligan takes off, sinewy and confident, Monk enjoying himself over Ware's propulsive line. Magnificent music. ‘Sweet and Lovely’ opens as a dirge but perks up as Mulligan softens his sound and Monk splashes around in the melodic deep end. There are alternative takes [nos 1 and 2] included for ‘I Mean You’ – take 4 was the original choice and it's here.

The bonus track is from the Newport Jazz Festival, poorly recorded but fun to have, Mulligan and Sims on form as ever. The Penguin Guide To Jazz On CD summed up the studio session as ‘Not an entirely probable encounter’ and that may be so, but it was evidently one that pleased all concerned. An imperative purchase for the open-minded, its smart digipack format and decent digital remastering further reasons to buy.