Boss CE-20 Chorus Ensemble. The CE-20 Chorus Ensemble is the culmination of over 25 years of BOSS chorus experience. This programmable chorus pedal not only models classics like the CE-1 and SDD-320, but creates entirely new effects including chorus for bass and acoustic guitar. New ?Brilliance? and ?Ambience? knobs offer unprecedented realtime control over the chorus tone-making the CE-20 a pedal no guitarist should be without.