The long extant duo of Nic Collins and Birgit Ulher applies two differing approaches to the trumpet, one electronic, and one purely analog. Collins uses a computer to imitate hacked circuits and Ulher applies everyday objects to her instrument to alter its sonic properties. Even with these seemingly opposite systems, it's difficult to tell who is doing what, and the combination often melds into one organic mass of constantly morphing sounds.

To be sure there are "normal" trumpet sonics here, deployed at key points in the array and often sounding like they've arrived via an old dusty 78 rpm record, overlaid with blankets of static and distortion. At other points the vibrating air column is subject to glitch and atomization, tuned in on a faulty shortwave radio whose signal isn't quite locked in. The gamut of sound here is often quite surprising, and the textures are thoughtfully chosen to enmesh or simply rub against each other.

As with much good, improvised music, it can sound like the product of one mind and one pair of hands, so carefully are the sounds deployed. My favorite section is probably the beginning of "Scudding" with its boiling air and metal rattle amid shy hisses and long-winded bubble. An alien signal pops in and out. Events arrive and mutate so quickly that it's difficult to catalogue them, so I'll stop trying. Suffice it to say that Spark Gap is as fine an example of modern improvisation as can be had anywhere, and you'd be best pleased to investigate it.