Incidentally, "The Voca People" is a performance piece--of the "Blue Man Group" ilk.

From the website:

The Voca People is a new international vocal theater performance that combines amazing vocal sounds and an acapella singing with the art of modern beat-box which imitates the sounds of drums, trumpets, guitars and other instruments and musical effects without using any musical instrument on stage, performed in a humoristic way and with audience participation.

Who are The Voca People?
The Voca people are 8 friendly aliens from the planet Voca, a musical planet that has no verbal communication but use vocal expressions only. They have heard the music from earth for decades now and with their imitation abilities they have decided to pay a one evening tribute to humanity and to perform the songs they love as musical- gratitude.