In Harmony is an Electro-Harmonix Voice Box demo video.

The Voice Box is an intelligent vocal harmony machine/ vocoder. Details below.

via EHX:

The Voice Box packs a multi-functional vocal synth processor into a tough and compact chassis. Sing, and you’ll have a troupe of backup singers following you in perfect harmony. Or use the built-in vocoder to unleash classic synth-robot sounds.

Diana Ross had the Supremes, Brian Wilson had the Beach Boys, Kraftwerk had The Robots. You have the Voice Box.

The harmony processor creates 2- to 4-part harmonies directly from your vocals, in the same key as your accompanying instrument. Studio-quality reverb lets you independently add depth to your dry and harmony vocals.

The focused 256-band articulate vocoder, designed by the same EMS genius who made vocoding famous, features adjustable harmonic enhancement and controllable formant shift.

Plug in your mic and your instrument, and let your new voice — or voices — be heard!

* Harmonically matches any electric instrument you plug into it

* Professional quality pitch shifting algorithm produces realistic harmonies

* The Low & High Harmony independently produces two harmony notes: 3rd and 5th

* 9 accessible programmable presets

* Natural Glissando

* Gender Bender knob allows for male/female formant modification

* Built-In Mic Pre with Phantom Power & Gain Switch

* Balanced XLR Line Output: Interface directly with any mixing board or A/D converter

* US96DC-200BI power supply included