Davis’ specter also lurks over Isotope 217, an electro-acoustic funk-jazz collaboration with Mazurek, Parker, bassist Matthew Lux and drummers John Herndon and Dan Bitney from fellow prolific Chicago sonic experimenters Tortoise. Isotope’s third proper album, Who Stole the Walkman?, is the happy medium between the Trio’s moody acoustic interplay and the duo’s playful electronic spirit. Walkman? is also Isotope’s most unfocused record, flitting between electronic process-as-composition pieces like “Moonlex” to live, call-and-response Miami booty-bass workouts like “[rewind].” If you are new to Isotope’s world, instead of Walkman? start with its excellent free-funk-jazz 1997 debut, The Unstable Molecule, which featured talented trombonist Sarah P. Smith, who had to leave the band due to health problems.