Also known as audio art, sound art developed in the late 1970s, though artists and musicians had been experimenting with sound and electronic music for decades prior. Sound art, like video art, is a medium rather than a style, and features many different types of sounds—from natural to man-made. The Italian artist Luigi Rus-solo (1883—1947) wrote a manifesto titled The Art of Noises in 1913, using new musical instruments as well as music comprised of “noise-sounds.” Also in 1913, Dada artist Marcel Duchamp created the Erratum Musical and later, Yves Klein wrote The Monotone Symphony (1947), which was composed of only one note. There are a number of sound artists (and visual artists who incorporate sound) working today, including the British artist Brian Eno (1948–), who collaborated with the artist Peter Schmidt to create an artwork called Oblique Strategies: Over One Hundred Worthwhile Dilemmas (1975). Oblique Strategies is a set of cards designed to assist in solving difficult dilemmas that arise during life and creative work, such as writing a musical composition. Sound art is still in its infancy, and new audio and digital technology continues to develop and impact the medium.