As producer Martin Davidson points out in his notes to Vortices and Angels, guitarist Derek Bailey (born 1930), saxophonist John Butcher (1954) and harpist Rhodri Davies (1971) represent three generations of improvisers on the London scene. Accordingly, Butcher’s duets with Bailey and Davies on the Emanem disc trace an arc from the assertively nonidiomatic approach Bailey developed in the ’60s, to the chamber-music-informed filigrees currently favored by Davies and contemporaries such as cellist Mark Wastell. Despite rapid, jarring shifts of timbres and dynamics, there is an incessant rhythmic prodding between Butcher’s tenor and Bailey’s amplified guitar throughout the nearly half-hour “Low Vortex” that exemplifies their common ground as improvisers, a dichotomous mix of responsiveness and counterintuition. Butcher and Davies interact in a more conscientiously complementary manner, particularly when Butcher’s tenor multiphonics and Davies’ textures hover about each other to create an otherworldly soundscape on “Rhagymadrodd,” an approach rooted in their work together in pianist Chris Burn’s Ensemble. The idea of putting these contrasting sessions together was inspired, as they simultaneously give the listener a glimpse of the diversity within the London scene and its intricate genealogies.