Like the affiliated moving parts of Swiss artist Jean Tinguely's kinetic sculpture, members of the Paris-based quintet Hubbub create sounds that vibrate in their own spheres, while also intertwined. Together since 1999 these two tracks recorded for Hubbub's 20th anniversary are prime representations of the band's improvisations. Hubbub consists of alto saxophonist Jean-Luc Guionnet, pianist Frédéric Blondy, guitarist Jean-Sébastien Mariage and percussionist Edward Peraud from France plus Swiss tenor saxophonist Bertrand Denzler.

Both the extended "abb" and the briefer "abb abb" vibrate on top of a seemingly endless drone that is foregrounded or backgrounded and at points is so concentrated it's almost opaque. Created by overlapping each instruments' timbres, its rumbling presence doesn't preclude individual expression. Most prevalent are Blondy's subtle single clips, key slaps and multi-note cascades, then intermittent guitar frails and buzzing flanges, while the percussionist is mostly limited to brief bell shakes, jagged cymbal scours and a resonating drum thwack at the conclusion.

Whether expressing diverse pitches with mewling cries or progressive toneless breaths the saxophonists are constantly featured however. But whether with pointed intersection or alone expressing squeezes, doits or multiphonics, reed output is always connected to what timbres the others are simultaneously shaking, stropping or squeaking. More obvious solo interludes are on "abb abb" but yearning reed trills, string or keyboard stops and percussion pressure are as wedded to group dynamics as the concentrated blend on "abb".

Creating an improvisational archetype is now established for Hubbub. Because of that it would now be advantageous to hear how the quintet sounded on its 25th anniversary as well as today.