Distant Voices Theremin by Widara

 The Wikipedia explains:

The theremin /ˈθɛrəmɪn/, originally known as the ætherphone/etherphone, thereminophone or termenvox/thereminvox is an early electronic musical instrument controlled without discernible 
physical contact from the player.

It is named after its Russian inventor, Professor Léon Theremin, who patented the device in 1928. 
The controlling section usually consists of two metal antennas which sense the position of the 
player's hands and control oscillators for frequency with one hand, and amplitude (volume) 
with the other, so it can be played without being touched. The electric signals from the theremin 
are amplified and sent to a loudspeaker.

But as you can see our Distant Voices Theremin is simplified version and can be easily used 
at a Rock concert. Have a fun!