Outside of the David S. Ware Quartet, Ware and his trusty pianist Matthew Shipp played in duo formation on only a handful of occasions, making this second instalment of AUM Fidelity's dedicated David S. Ware Archive series a very valuable document indeed. Their two-part improvisation, ‘Tao Flow’, unfolds over 40 minutes as a seamless stretch of sound, Ware's tenor hugging an ardent, cry-point falsetto as Shipp's hymning tremolos and his muscular, malleable vamps remap the waves of energy underneath. Ware moves largely by stealth. A mighty procession of lines – some pursued with the doggedness of a taxman, others flirted with then abandoned – have been excavated from deep fundamental beliefs about how open-plan improvisation and raw blues can coexist; briefly chancing upon the opening bars of ‘Sweet and Lovely’, Ware twists the notes out of alignment then runs the other way. The emerging terrain feels pretty equally divided. A peculiarly lovely moment pops up out of nowhere as Shipp sustains chords on strings inside his piano, bleaching the harmony with a sound like a pure-toned harpsichord. When Ware subsequently plunges into his low register, Shipp works his way towards an athletic, chromatically wayward stride piano that reasserts itself during the second part as their duologue becomes ever more fluid, running on well-honed instinct. An exit strategy is negotiated as corkscrew saxophone loops bump into cathartic chorales. And, finally, that energy flow gets brutally cut and a clearly mesmerised audience roars its approval.