by Sean Westergaard   Frequency are a Chicago all-star quartet of AACM-associated jazz players: Ed Wilkerson (woodwinds), Nicole Mitchell (flutes, piccolo), Harrison Bankhead (bass, cello), and Avreeayl Ra (drums, percussion). Wilkerson and Bankhead have a long history together; Ra and Bankhead played together with both Michael Mason and Malachi Thompson; and all have crossed paths as members of the AACM (Nicole Mitchell is co-president). They came together as a quartet and released their self-titled debut in 2006 on Thrill Jockey.