The Voice Box Vocal Harmony Machine/Vocoder from Electro-Harmonix is a multi-functional vocal synth processor. The Voice Box allows you to products 1 to 4 part harmonies from the solo vocals. The harmonies are determined by the chords played on your instrument and the notes you sing. The Voice Box has an easy-to-use vocoder, allowing you to easily create classic vocoder sounds. Additionally, the Voice Box has an Octave mode, Whistle effect and a Unison effect.