Out of town – and even in Europe – individually these musicians are headliners, but in Chicago locals can catch sets by the Extraordinary Popular Delusions (EPD) quartet every Monday night in a pass-the-hat situation. In this brief preview for an upcoming gig, The Chicago Reader’s Bill Meyer reports on the ESP evident in the EPD’s improvised performances. That’s because its members – Mars Williams on alto and tenor saxophones, percussion, zither and toys; Jim Baker on electric piano, synthesizer and viola; Brian Sandstrom, who play bass, electric guitar and trumpet; and Steve Hunt, an expert on drums, percussion and waterphone – have had a weekly quartet gig at one or another Chicago nightspot since 2005. All of the players have extensive experience on their own or working with one another in bands like the NRG Ensemble. The only fact missing in the story is that tenor saxophonist Ed Wilkerson Jr. regularly sits in for Williams when the latter is unavailable.