The contact between electronic sound and live instrumental sound, and the contact of the moment 'now'.
Contacte means contact. It is the contact between the electronic sound and the live player (instrumental sound), and also the contact of each moment of what Stockhausen calls the 'instant form'.
Regarding the 'momentary form,' Stockhausen said in a late-night music program on West German Radio in Cologne on January 12, 1961: "In recent years, a lot of music has been composed that is far from a form with a dramatic finale. There are no climaxes, no signs of climaxes, and no stages of development in these works. Rather, they suddenly and violently build up and try to maintain the 'peak' until the end of the work. It is always at a maximum or minimum, and the listener cannot predict how the piece will progress. It is not a moment that is part of a passage, nor is it a part of a constant duration. The concentration on the 'now' creates a vertical line that breaks the horizontal concept of time and leads us to the timeless..."
As the listener listens to the booming sounds coming from various directions, dark noises, percussion instruments, piano sounds, etc., the listener is freed from this world dominated by time flowing inexorably, and has a very dense and mysterious musical experience.
There are two versions of "Contacte": one for electronic sounds only, and the other for electronic instruments, piano, and percussion.