Since 1974, Bead records has been collecting and disseminating fine examples of improvised music, and here we have another beautiful turn. Emil Karlsen plays drums while Lawrence Casserley applies his signal processing instrument, and a bit of black magic ensues. A live duet with altered echoes and quick thinking galore, you'd be forgiven if you happened to forget that there's only one physical player and not an army of charging gremlins.

It's fascinating to witness Karlsen's playing, and Casserley's playing of Karlsen's playing — repeating, stretching, smashing and filtering percussive elements to add an otherworldliness in real time. Imagine a legion of drummers in a mirrored funhouse, curled and warped in ever new ways as you shift your position. There's an enormous amount here that sounds like sonic weather fronts rising and falling in slow weighted routes, while smallish detritus gets picked up and blown about.

This recording reminds me very much of Bob Ostertag's "Getting A Head", wherein he processes the percussion of Charles K. Noyes using an altogether more arcane system. Both recordings play with time and memory, and do so in inventive and careful ways. This is such fertile ground that I'm surprised that there are so few practitioners of it.