Karlheinz Stockhausen began Klavierstück X in 1954 as part of the set of pieces comprising Composition No. 4. Though most of the set was completed and premiered in 1955, Stockhausen substantially revised Klavierstück X (as well as IX) in 1961, following his experience with such works as Klavierstück XI (1956), Kontakte (1959 - 60), and other works that grew from his study of the behavior of sound in the Cologne electronic music studio. At times, Klavierstück X is dense with activity, while at others, Stockhausen employs complete silence. The sonic materials of the piece include elements Stockhausen had previously used only incidentally or infrequently: tone clusters, glissandi, trills and tremolos, grace notes, resonance effects, and so on. As in Klavierstück IX--but here, more deliberately--the world of the electronic studio is represented in this work. Silences may represent a dropout of signal, for example, and closely spaced chords sound like ring-modulated tones. Klavierstück X may be thought of, in fact, as representing the devices of Kontakte in a distillation for solo piano.
Klavierstück X was completed in 1961 and premiered by Aloys Kontarsky in the following year. [allmusic.com]