Few composers were as influential in the second half of the 20th century as Karlheinz Stockhausen (born 1928). His music has had an effect across a wide

Few composers were as influential in the second half of the 20th century as Karlheinz Stockhausen (born 1928). His music has had an effect across a wide range of genres, from chamber music and opera to rock (he's in the cover collage of the Beatles' Sgt. Pepper's Lonely Hearts Club Band) and the underground dance scene (witness his cameo appearance in the film Modulations).

As one of the most well-known post-WWII composers, Stockhausen became famous for his structurally rigorous approach to music. He was heavily influenced by Austrian 12-tone composer Anton Webern, who used number theory to control the parameters of a musical work. Stockhausen would take things a step further and look for ways to control every aspect of sound.

At the Cologne studio, where he studied from 1947 to 1951, Stockhausen helped pioneer elektronische musik (electronic music), which stood in stark contrast to the collage aspects of musique concrète being developed in France by Pierre Schaeffer. Using pure electronic sound, Stock-hausen found that he could order and serialize every conceivable musical parameter: frequency, duration, intensity, timbre, attack and decay.

His earliest electronic pieces were created using sine waves, white noise and electrical pulses. For example, in Studie I (1953), Stock-hausen carefully combined sine waves to create complex timbres in an early form of additive synthesis. Later, he combined electronic sounds with concrete elements to create two of the genre's most important works, Gesang der Jünglinge (Song of the Youths; 1955-56) and Hymnen (Anthems; 1967). Other important works include Kontakte (1959-60) for tape, piano and percussion; Mikrophonie I (1964) for tam-tam and live processing; and Telemusik (1966), a 5-channel work created at the NHK radio studio in Tokyo. Stockhausen often refers to himself as a sound projectionist, and he even developed a mechanical system to move sound around a room in real time, using a speaker mounted on a rotating table with microphones circling it.

In more than 50 years of composing, Stock-hausen has explored just about every orchestration you can imagine, from music for music boxes, Tierkreis (1974), to the semirecent Helicopter String Quartet (1992-93). His operatic works are Wagnerian in scale, with an opera assigned to each day of the week. Stockhausen's text pieces Aus den Sieben Tagen (From the Seven Days; 1968) were intended to be played in a meditational context, though they are somewhat reminiscent in style to the Fluxus works of La Monte Young and Yoko Ono. (Stockhausen's texts, however, instruct the performer to engage in challenging “musical” activities as opposed to other kinds of performance events.) One of the instructions in Aufwärts (from Aus den Sieben Tagen) reads, “Play a vibration in the rhythm of the universe.” When a musician asked how he would know when he was playing in the rhythm of the universe, Stock-hausen replied, “I will tell you.”

That air is inextricably linked with Stockhausen, who has long been an outspoken and controversial figure in contemporary music. After studying with the composer in the '50s, Cornelius Cardew wrote a particularly damning critique titled “Stockhausen Serves Imperialism.” More recently, after the events of 9/11, it was reported that Stockhausen had metaphorically referred to the terrorist attacks as “the greatest work of art ever.” He immediately retracted the remark, but concerts of his music were subsequently postponed or canceled around the world. Nevertheless, Stock-hausen's body of work remains pivotal to today's sonic experimentalists.

Composer-supervised recordings of Stock-hausen's music — as well as scores, videos and books about Stockhausen's music — are available from Stockhausen-Verlag (www.stockhausen.org). Although they are a bit pricey, the CDs come with elaborately detailed booklets that offer a unique view into the mind of this important composer.

Stockhausen-Verlag; Kettenberg 15, Kürten, Germany 51515; fax 49-2268-1813.