The Electro-Harmonix USA Bassballs Effects Pedal is a twin dynamic envelope follower for electric bass and guitar. Bassballs uses 2 critically tuned, sweeping dynamic filters that respond sensitively to attack variations creating shifting peaks and notches to produce vowel-like overtones. The switchable distortion mode's warm harmonic distortion intensifies the overtones and deep resonance of the effect. The Envelope Follower's sensitivity control determines how sensitive the filters are to playing dynamics and lets the musician tailor Bassballs' sound to the output level of a particular instrument. This Electro-Harmonix effects pedal is housed in the original-style steel chassis and packaged in a distinctive pine box.