Over the past 20 years, duo recordings have become more common in jazz, but when a horn or a voice is involved, the instrumental partner is likely to be a piano. Few guitarists are capable of providing the rhythmic thrust and nuance, the harmonic richness and judgment required to sustain performances in which both participants are left with no hiding places, no safety net. Joe Pass is one of the few. His Pablo duo albums with Ella Fitzgerald make that quite clear. So, too, does this one with J.J. Johnson, the leading trombonist of his generation. Pass's neural synapses, reaction times, and right brain/left brain connections could not be approximated by linking all of the world's supercomputer centers. He gives Johnson the support and inspiration he might expect from a symphony orchestra, without the excess baggage. This is improvised chamber music of the highest order by two of the greatest virtuosos of their time.