And just like rock, the only element keeping wildly different music under the same umbrella is the main instrument. With rock, it was the guitar. With electronica, it is the microchip. Electronica is any kind of music made mostly with microprocessors, anything from drum machines to computer voice programs. This doesn't mean electronica has no other instruments.
Most songs have vocalists.
But the German band Kraftwerk are generally acknowledged as the pioneers of the form. The breakthrough came when musicians realized that though the music is mechanical by nature, it doesn't have to sound that way. Indeed, a soaring, soulful vocal has become almost an essential element for a club hit. House is the official music of the club scene in most major cities. The idea is to keep the crowd dancing with continuous tunes that segue smoothly into each other.