Ryoji Ikeda (born 1966) is a Japanese sound artist who lives and works in Paris. Ikeda's music is concerned primarily with sound in a variety of "raw" states, such as sine tones and noise, often using frequencies at the edges of the range of human hearing. The conclusion of his album +/- features just such a tone; of it, Ikeda says "a high frequency sound is used that the listener becomes aware of only upon its disappearance" (from the CD booklet). Rhythmically, Ikeda's music is highly imaginative, exploiting beat patterns and, at times, using a variety of discrete tones and noise to create the semblance of a drum machine. His work also encroaches on the world of ambient music; many tracks on his albums are concerned with slowly evolving soundscapes, with little or no sense of pulse.