Editing Karlheinz Stockhausen (section)

==Compositions==
{{See also|List of compositions by Karlheinz Stockhausen}}
Stockhausen wrote 370 individual works. He often departs radically from musical tradition and his work is influenced by [[Olivier Messiaen]], [[Edgard Varèse]], and [[Anton Webern]], as well as by film{{sfn|Stockhausen|1996b}} and by painters such as [[Piet Mondrian]]{{sfn|Stockhausen|1996a|loc=94}}{{sfn|Stockhausen ''Texte''|loc=3:92–93}}{{sfn|Toop|1998}} and [[Paul Klee]].{{sfn|Maconie|2005|loc=187}}

===1950s===
Stockhausen began to compose in earnest only during his third year at the conservatory.{{sfn|Kurtz|1992|loc=26–27}} His early student compositions remained out of the public eye until, in 1971, he published ''[[Chöre für Doris]]'', ''[[Drei Lieder (Stockhausen)|Drei Lieder]]'' for alto voice and chamber orchestra, ''Choral'' for a cappella choir (all three from 1950), and a [[Sonatine (Stockhausen)|Sonatine]] for violin and piano (1951).{{sfn|Maconie|1990|loc=5–6, 11}}

In August 1951, just after his first Darmstadt visit, Stockhausen began working with a form of [[Theme (music)|athematic]] [[serialism|serial]] composition that rejected the [[twelve-tone technique]] of [[Arnold Schoenberg|Schoenberg]].{{sfn|Felder|1977|loc=92}} He characterized many of these earliest compositions (together with the music of other, like-minded composers of the period) as ''[[Punctualism|punktuelle Musik]]'', "punctual" or "pointist" music, commonly mistranslated as "pointillist", though one critic concluded after analysing several of these early works that Stockhausen "never really composed punctually".{{sfn|Sabbe|1981}} Compositions from this phase include ''[[Kreuzspiel]]'' (1951), the ''[[Klavierstücke (Stockhausen)|Klavierstücke I–IV]]'' (1952—the fourth of this first set of four ''Klavierstücke'', titled ''Klavierstück IV'', is specifically cited by Stockhausen as an example of "punctual music",{{sfn|Stockhausen ''Texte''|loc=2:19}} and the first (unpublished) versions of ''[[Punkte]]'' and ''Kontra-Punkte'' (1952).{{sfn|Stockhausen ''Texte''|loc=2:20}} However, several works from these same years show Stockhausen formulating his "first really ground-breaking contribution to the theory and, above all, practice of composition", that of "group composition", found in Stockhausen's works as early as 1952 and continuing throughout his compositional career.{{sfn|Toop|2005|loc=3}} This principle was first publicly described by Stockhausen in a radio talk from December 1955, titled "Gruppenkomposition: ''[[Klavierstücke (Stockhausen)|Klavierstück I]]''".{{sfn|Stockhausen ''Texte''|loc=1:63–74}}

In December 1952, he composed a ''Konkrete Etüde'', realized in [[Pierre Schaeffer]]'s Paris [[musique concrète]] studio. In March 1953, he moved to the NWDR studio in Cologne and turned to [[electronic music]] with two ''[[Studie II|Electronic Studies]]'' (1953 and 1954), and then introducing spatial placements of sound sources with his mixed ''concrète'' and electronic work ''[[Gesang der Jünglinge]]'' (1955–56). Experiences gained from the ''Studies'' made plain that it was an unacceptable oversimplification to regard timbres as stable entities.{{sfn|Stockhausen ''Texte''|loc=1:56}} Reinforced by his studies with Meyer-Eppler, beginning in 1955, Stockhausen formulated new "statistical" criteria for composition, focussing attention on the [[Aleatoric music|aleatoric]], directional tendencies of sound movement, "the change from one state to another, with or without returning motion, as opposed to a fixed state".{{sfn|Decroupet and Ungeheuer|1998|loc=98–99}} Stockhausen later wrote, describing this period in his compositional work, "The first revolution occurred from 1952/53 as ''musique concrète'', ''electronic tape music'', and ''space music'', entailing composition with transformers, generators, modulators, magnetophones, etc; the integration of {{em|all}} concrete and abstract (synthetic) sound possibilities (also all noises), and the controlled projection of sound in space".<ref>{{harvnb|Stockhausen|1989b|loc=127}}, reprinted in {{harvnb|Schwartz, Childs, and Fox|1998|loc=374}}</ref> His position as "the leading German composer of his generation"{{sfn|Toop|2001}} was established with ''Gesang der Jünglinge'' and three concurrently composed pieces in different media: ''[[Zeitmaße]]'' for five woodwinds, ''Gruppen'' for three orchestras, and ''[[Klavierstücke (Stockhausen)|Klavierstück XI]]''.{{sfn|Kohl|1998a|loc=61}} The principles underlying the latter three compositions are presented in Stockhausen's best-known theoretical article, "... wie die Zeit vergeht ..." ("... How Time Passes ..."), first published in 1957 in vol. 3 of ''[[Die Reihe]]''.{{sfn|Stockhausen ''Texte''|loc=1:99–139}}

His work with electronic music and its utter fixity led him to explore modes of instrumental and vocal music in which performers' individual capabilities and the circumstances of a particular performance (e.g., hall acoustics) may determine certain aspects of a composition. He called this "variable form".{{sfn|Wörner|1973|loc=101–105}} In other cases, a work may be presented from a number of different perspectives. In ''[[Zyklus]]'' (1959), for example, he began using [[graphic notation (music)|graphic notation]] for instrumental music. The [[Sheet music|score]] is written so that the performance can start on any page, and it may be read upside down, or from right to left, as the performer chooses.{{sfn|Stockhausen ''Texte''|loc=2, 73–100}} Still other works permit different routes through the constituent parts. Stockhausen called both of these possibilities "polyvalent form",{{sfn|Stockhausen ''Texte''|loc=1:241–251}} which may be either [[Aleatoric music#"Open form" chance music|open form]] (essentially incomplete, pointing beyond its frame), as with ''Klavierstück XI'' (1956), or "closed form" (complete and self-contained) as with ''Momente'' (1962–64/69).{{sfn|Kaletha|2004|loc=97–98}}

In many of his works, elements are played off against one another, simultaneously and successively: in ''Kontra-Punkte'' ("Against Points", 1952–53), which, in its revised form became his official "opus 1", a process leading from an initial "point" texture of isolated notes toward a florid, ornamental ending is opposed by a tendency from diversity (six timbres, dynamics, and durations) toward uniformity (timbre of solo piano, a nearly constant soft dynamic, and fairly even durations).{{sfn|Stockhausen ''Texte''|loc=2, 20–21}} In ''Gruppen'' (1955–57), fanfares and passages of varying speed (superimposed durations based on the [[harmonic series (music)|harmonic series]]) are occasionally flung between three full orchestras, giving the impression of movement in space.{{sfn|Maconie|2005|loc=486}}

In his ''[[Kontakte]]'' for electronic sounds (optionally with piano and percussion) (1958–60), he achieved for the first time an [[isomorphism]] of the four parameters of pitch, duration, dynamics, and timbre.{{sfn|Stockhausen|1962|loc=40}}

===1960s===
In 1960, Stockhausen returned to the composition of vocal music (for the first time since ''Gesang der Jünglinge'') with ''[[Carré (Stockhausen)|Carré]]'' for four orchestras and four choirs.{{sfn|Stockhausen-Verlag|2010|loc=18}} Two years later, he began an expansive [[cantata]] titled ''Momente'' (1962–64/69), for solo soprano, four choir groups and thirteen instrumentalists.{{sfn|Stockhausen-Verlag|2010|loc=18}} In 1963, Stockhausen created ''[[Plus-Minus (Stockhausen)|Plus-Minus]]'', "2 × 7 pages for realisation" containing basic note materials and a complex system of transformations to which those materials are to be subjected in order to produce an unlimited number of different compositions.{{sfn|Stockhausen-Verlag|2010|loc=20}}{{sfn|Toop|2005|loc=175–178}} Through the rest of the 1960s, he continued to explore such possibilities of "[[process music|process composition]]" in works for live performance, such as ''Prozession'' (1967), ''[[Kurzwellen]]'', and ''[[Spiral (Stockhausen)|Spiral]]'' (both 1968), culminating in the verbally described "intuitive music" compositions of ''[[Aus den sieben Tagen]]'' (1968) and ''[[Für kommende Zeiten]]'' (1968–70).{{sfn|Fritsch|1979}}{{sfn|Kohl|1981|loc=192–193, 227–251}}{{sfn|Kohl|1998b|loc=7}}{{sfn|Toop|2005|loc=191–192}} Some of his later works, such as ''[[Ylem (Stockhausen)|Ylem]]'' (1972) and the first three parts of ''[[Herbstmusik]]'' (1974), also fall under this rubric.{{sfn|Maconie|2005|loc=254, 366–368}} Several of these process compositions were featured in the all-day programmes presented at Expo 70, for which Stockhausen composed two more similar pieces, ''Pole'' for two players, and ''Expo'' for three.{{sfn|Kohl|1981|loc=192–193}}{{sfn|Maconie|2005|loc=323–324}} In other compositions, such as ''Stop'' for orchestra (1965), ''[[Adieu (Stockhausen)|Adieu]]'' for wind quintet (1966), and the ''Dr. K Sextett'', which was written in 1968–69 in honour of Alfred Kalmus of Universal Edition, he presented his performers with more restricted improvisational possibilities.{{sfn|Maconie|2005|loc=262, 267–268, 319–320}}

He pioneered live electronics in ''[[Mixtur]]'' (1964/67/2003) for orchestra and electronics,{{sfn|Kohl|1981|loc=51–163}} ''[[Mikrophonie (Stockhausen)|Mikrophonie I]]'' (1964) for [[tam-tam]], two microphones, two filters with [[potentiometer]]s (6 players),{{sfn|Maconie|1972}}{{sfn|Maconie|2005|loc=255–257}} ''[[Mikrophonie (Stockhausen)|Mikrophonie II]]'' (1965) for choir, [[Hammond organ]], and four [[Ring modulation|ring modulators]],{{sfn|Peters|1992}} and ''Solo'' for a melody instrument with feedback (1966).{{sfn|Maconie|2005|loc=262–265}} Improvisation also plays a part in all of these works, but especially in ''Solo''.{{sfn|Maconie|2005|loc=264}} He also composed two electronic works for [[Tape recorder|tape]], ''Telemusik'' (1966) and ''[[Hymnen]]'' (1966–67).{{sfn|Kohl|2002}}{{sfn|Stockhausen-Verlag|2010|loc=21}} The latter also exists in a version with partially improvising soloists, and the third of its four "regions" in a version with orchestra.{{sfn|Stockhausen-Verlag|2010|loc=21}} At this time, Stockhausen also began to incorporate pre-existent music from world traditions into his compositions.{{sfn|Kohl|1981|loc=93–95}}{{sfn|Stockhausen ''Texte''|loc=4, 468–476}} ''Telemusik'' was the first overt example of this trend.{{sfn|Kohl|2002|loc=96}}

In 1968, Stockhausen composed the vocal sextet ''[[Stimmung]]'', for the [[Collegium Vocale Köln]], an hour-long work based entirely on the [[overtone]]s of a low [[B♭ (musical note)|B-flat]].{{sfn|Toop|2005|loc=39}} In the following year, he created ''[[Fresco (Stockhausen)|Fresco]]'' for four orchestral groups, a ''Wandelmusik'' ("foyer music") composition.{{sfn|Maconie|2005|loc=321}} This was intended to be played for about five hours in the foyers and grounds of the Beethovenhalle auditorium complex in [[Bonn]], before, after, and during a group of (in part simultaneous) concerts of his music in the auditoriums of the facility.{{sfn|Maconie|2005|loc=321–323}} The overall project was given the title ''Musik für die Beethovenhalle''.{{sfn|Maconie|2005|loc=296}} This had precedents in two collective-composition seminar projects that Stockhausen gave at Darmstadt in 1967 and 1968: ''Ensemble'' and ''Musik für ein Haus'',{{sfn|Gehlhaar|1968}}{{sfn|Ritzel|1970}}{{sfn|Iddon|2004}}{{sfn|Maconie|2005|loc=321}} and would have successors in the "park music" composition for five spatially separated groups, ''[[Sternklang]]'' ("Star Sounds") of 1971, the orchestral work ''Trans'', composed in the same year and the thirteen simultaneous "musical scenes for soloists and duets" titled ''[[Alphabet für Liège]]'' (1972).{{sfn|Maconie|2005|loc=334–336, 338, 341–343}}

===Space music and Expo '70===
[[File:Osaka Expo'70 Korean Pavilion.jpg|thumb|The German Pavilion at Expo '70 (the spherical auditorium is out of view to the right)]]
Since the mid-1950s, Stockhausen had been developing concepts of [[spatial music|spatialization]] in his works, not only in electronic music, such as the 5-channel ''[[Gesang der Jünglinge]]'' (1955–56) and ''[[Telemusik]]'' (1966), and 4-channel ''[[Kontakte]]'' (1958–60) and ''[[Hymnen]]'' (1966–67). Instrumental/vocal works like ''Gruppen'' for three orchestras (1955–57) and ''Carré'' for four orchestras and four choirs (1959–60) also exhibit this trait.{{sfn|Stockhausen ''Texte''|loc=2:71–72, 49–50, 102–103}}{{sfn|Stockhausen|1989a|loc=105–108}}{{sfn|Cott|1973|loc=200–201}} In lectures such as "Music in Space" from 1958,{{sfn|Stockhausen ''Texte''|loc=1:152–175}} he called for new kinds of concert halls to be built, "suited to the requirements of spatial music". His idea was {{Blockquote|a spherical space which is fitted all around with loudspeakers. In the middle of this spherical space a sound-permeable, transparent platform would be suspended for the listeners. They could hear music composed for such standardized spaces coming from above, from below and from all points of the compass.{{sfn|Stockhausen ''Texte''|loc=1:153}}}} In 1968, the [[West Germany|West German]] government invited Stockhausen to collaborate on the German Pavilion at the [[Expo '70|1970 World Fair]] in [[Osaka]] and to create a joint multimedia project for it with artist [[Otto Piene]]. Other collaborators on the project included the pavilion's architect, [[Fritz Bornemann]], Fritz Winckel, director of the Electronic Music Studio at [[Technische Universität Berlin]], and engineer Max Mengeringhausen. The pavilion theme was "gardens of music", in keeping with which Bornemann intended "planting" the exhibition halls beneath a broad lawn, with a connected auditorium "sprouting" above ground. Initially, Bornemann conceived this auditorium in the form of an [[amphitheatre]], with a central orchestra podium and surrounding audience space. In the summer of 1968, Stockhausen met with Bornemann and persuaded him to change this conception to a spherical space with the audience in the centre, surrounded by loudspeaker groups in seven rings at different "latitudes" around the interior walls of the sphere.{{sfn|Kurtz|1992|loc=166}}{{sfn|Föllmer|1996}}

Although Stockhausen and Piene's planned multimedia project, titled ''Hinab-Hinauf'', was developed in detail,{{sfn|Stockhausen ''Texte''|loc=3:155–174}} the World Fair committee rejected their concept as too extravagant and instead asked Stockhausen to present daily five-hour programs of his music.{{sfn|Kurtz|1992|loc=178}} Stockhausen's works were performed for 5½ hours every day over a period of 183 days to a total audience of about a million listeners.{{sfn|Wörner|1973|loc=256}} According to Stockhausen's biographer, Michael Kurtz, "Many visitors felt the spherical auditorium to be an oasis of calm amidst the general hubbub, and after a while it became one of the main attractions of Expo 1970".{{sfn|Kurtz|1992|loc=179}}

===1970s===
[[File:Shiraz 37.jpg|thumb|Stockhausen (front centre) at the mixing desk for a performance by [[Aloys and Alfons Kontarsky|Alfons and Aloys Kontarsky]] of ''Mantra'', [[Shiraz Arts Festival]], Iran, 1972]]
Beginning with ''[[Mantra (Stockhausen)|Mantra]]'' for two pianos and electronics (1970), Stockhausen turned to [[formula composition]], a technique which involves the projection and multiplication of a single, double, or triple [[melody|melodic]]-line formula.{{sfn|Kohl|1983–84a}}{{sfn|Kohl|1990}}{{sfn|Kohl|2004}} Sometimes, as in ''Mantra'' and the large orchestral composition with mime soloists, ''Inori'', the simple formula is stated at the outset as an introduction. He continued to use this technique (e.g., in the two related solo-clarinet pieces, ''Harlekin'' [Harlequin] and ''Der kleine Harlekin'' [The Little Harlequin] of 1975, and the orchestral ''[[Jubiläum]]'' [Jubilee] of 1977) through the completion of the opera-cycle ''Licht'' in 2003.{{sfn|Blumröder|1982}}{{sfn|Conen|1991}}{{sfn|Kohl|1983–84a}}{{sfn|Kohl|1990}}{{sfn|Kohl|1993}}{{sfn|Kohl|2004}}{{sfn|Stockhausen-Verlag|2010|loc=10}} Some works from the 1970s did not employ formula technique—e.g., the vocal duet "[[Alphabet für Liège#Indianerlieder|Am Himmel wandre ich]]" (In the Sky I am Walking, one of the 13 components of the multimedia ''Alphabet für Liège'', 1972, which Stockhausen developed in conversation with the British biophysicist and lecturer on mystical aspects of sound vibration [[Jill Purce]]), "Laub und Regen" (Leaves and Rain, from the theatre piece ''Herbstmusik'' (1974), the unaccompanied-clarinet composition ''[[Amour (Stockhausen)|Amour]]'', and the choral opera ''[[Atmen gibt das Leben]]'' (Breathing Gives Life, 1974/77)—but nevertheless share its simpler, melodically oriented style.{{sfn|Conen|1991|loc=57}}{{sfn|Kurtz|1992|loc=192–193}} Two such pieces, ''Tierkreis'' ("Zodiac", 1974–75) and ''[[In Freundschaft]]'' (In Friendship, 1977, a solo piece with versions for virtually every orchestral instrument), have become Stockhausen's most widely performed and recorded compositions.{{sfn|Anon.|2007a}}{{sfn|Deruchie|2007}}{{sfn|Nordin|2004}}

This dramatic simplification of style provided a model for a new generation of German composers, loosely associated under the label ''neue Einfachheit'' or [[New Simplicity]].{{sfn|Andraschke|1981}} The best-known of these composers is [[Wolfgang Rihm]], who studied with Stockhausen in 1972–73. His orchestral composition ''Sub-Kontur'' (1974–75) quotes the formula of Stockhausen's ''Inori'' (1973–74), and he has also acknowledged the influence of ''Momente'' on this work.{{sfn|Frobenius|1981|loc=53 + note 59–60}}

Other large works by Stockhausen from this decade include the orchestral ''[[Trans (Stockhausen)|Trans]]'' (1971) and two music-theatre compositions utilizing the ''Tierkreis'' melodies: ''[[Musik im Bauch]]'' ("Music in the Belly") for six percussionists (1975), and the science-fiction "opera" ''[[Sirius (Stockhausen)|Sirius]]'' (1975–77) for eight-channel electronic music with soprano, bass, trumpet, and bass clarinet, which has four different versions for the four seasons, each lasting over an hour and a half.{{sfn|Stockhausen-Verlag|2010|loc=24–25}}
[[File:Stockhausen March 2004 excerpt.jpg|thumb|upright|Stockhausen in 2004 during the mix-down of the recording of ''Angel Processions'' from ''[[Sonntag aus Licht]]'', in Sound Studio N, Cologne]]

===1977–2003===

{{Main|Licht}}
Between 1977 and 2003, Stockhausen composed seven operas in a cycle titled ''[[Licht|Licht: Die sieben Tage der Woche]]'' ("Light: The Seven Days of the Week").{{sfn|Maconie|2005|loc=403–544}} The ''Licht'' cycle deals with the traits associated in various historical traditions with each weekday (Monday = birth and fertility, Tuesday = conflict and war, Wednesday = reconciliation and cooperation, Thursday = traveling and learning, etc.) and with the relationships between three archetypal characters: [[Michael (archangel)|Michael]], [[Lucifer]], and [[Adam and Eve|Eve]].{{sfn|Kohl|1983–84b|loc=489}}{{sfn|Stockhausen ''Texte''|loc=6:152–156, 175, 200–201}} Each of these characters dominates one of the operas (''Donnerstag'' [Thursday], ''Samstag'' [Saturday], and ''Montag'' [Monday], respectively), the three possible pairings are foregrounded in three others, and the equal combination of all three is featured in ''Mittwoch'' (Wednesday).{{sfn|Kohl|1990|loc=274}}

Stockhausen's conception of opera was based significantly on ceremony and ritual, with influence from the Japanese [[Noh]] theatre,{{sfn|Stockhausen, Conen, and Hennlich|1989|loc=282}} as well as [[Judeo-Christian]] and [[Vedic mythology|Vedic]] traditions.{{sfn|Bruno|1999|loc=134}} In 1968, at the time of the composition of ''Aus den sieben Tagen'', Stockhausen had read a biography by [[Satprem]] about the Bengali guru [[Sri Aurobindo]],{{sfn| Guerrieri|2009}} and subsequently he also read many of the published writings by Aurobindo himself. The title of ''Licht'' owes something to Aurobindo's theory of "[[Agni]]" (the Hindu and Vedic fire deity), developed from two basic premises of nuclear physics; Stockhausen's definition of a formula and, especially, his conception of the ''Licht'' superformula, also owes a great deal to Sri Aurobindo's category of the "supramental".{{sfn|Peters|2003|loc=227}} Similarly, his approach to voice and text sometimes departed from traditional usage: Characters were as likely to be portrayed by instrumentalists or dancers as by singers, and a few parts of ''Licht'' (e.g., ''Luzifers Traum'' from ''Samstag'', ''Welt-Parlament'' from ''Mittwoch'', ''Lichter-Wasser'' and ''Hoch-Zeiten'' from ''Sonntag'') use written or improvised texts in simulated or invented languages.{{sfn|Kohl|1983–84b|loc=499}}{{sfn|Moritz|2005}}{{sfn|Stockhausen|1999|loc=18–25}}{{sfn|Stockhausen|2001b|loc=20}}{{sfn|Stockhausen|2003|loc=20}}

The seven operas were not composed in "weekday order" but rather starting (apart from ''Jahreslauf'' in 1977, which became the first act of ''Dienstag'') with the "solo" operas and working toward the more complex ones: ''Donnerstag'' (1978–80), ''Samstag'' (1981–83), ''Montag'' (1984–88), ''Dienstag'' (1977/1987–91), ''Freitag'' (1991–94), ''Mittwoch'' (1995–97), and finally ''Sonntag'' (1998–2003).{{sfn|Stockhausen-Verlag|2010|loc=3–7, 26–48}}

Stockhausen had dreams of flying throughout his life, and these dreams are reflected in the ''[[Helikopter-Streichquartett]]'' (the third scene of ''Mittwoch aus Licht''), completed in 1993. In it, the four members of a [[string quartet]] perform in four [[helicopter]]s flying independent flight paths over the countryside near the concert hall. The sounds they play are mixed together with the sounds of the helicopters and played through speakers to the audience in the hall. Videos of the performers are also transmitted back to the concert hall. The performers are synchronized with the aid of a [[click track]], transmitted to them and heard over headphones.{{sfn|Stockhausen|1996c|loc=215}}

The first performance of the piece took place in Amsterdam on 26 June 1995, as part of the [[Holland Festival]].{{sfn|Stockhausen| 1996c|loc=216}} Despite its extremely unusual nature, the piece has been given several performances, including one on 22 August 2003 as part of the [[Salzburg Festival]] to open the Hangar-7 venue,{{sfn|Stockhausen-Verlag|2010|loc=7}} and the German première on 17 June 2007 in [[Braunschweig]] as part of the Stadt der Wissenschaft 2007 Festival.{{sfn|Stockhausen-Stiftung|2007}} The work has also been recorded by the [[Arditti Quartet]].<ref>{{Cite web |title=STOCKHAUSEN: Helicopter String Quartet - Arditti Quartet (DVD) |url=https://www.classicselectworld.com/products/stockhausen-helicopter-string-quartet-arditti-quartet |access-date=2024-06-12 |website=ClassicSelect World |language=en}}</ref>

In 1999 he was invited by [[Walter Fink]] to be the ninth composer featured in the annual [[Rheingau Musik Festival#Portraits of living composers|Komponistenporträt]] of the [[Rheingau Musik Festival]].{{sfn|Rheingau Musik Festival|2017}}

In 1999, [[BBC]] producer Rodney Wilson asked Stockhausen to collaborate with [[Brothers Quay|Stephen and Timothy Quay]] on a film for the fourth series of Sound on Film International. Although Stockhausen's music had been used for films previously (most notably, parts of [[Hymnen]] in [[Nicolas Roeg]]'s ''[[Walkabout (film)|Walkabout]]'' in 1971), this was the first time he had been asked to provide music specially for the purpose. He adapted 21 minutes of material taken from his electronic music for ''Freitag aus Licht'', calling the result ''Zwei Paare'' (Two Couples), and the Brothers Quay created their animated film, which they titled ''[[In Absentia (film)|In Absentia]]'', based only on their reactions to the music and the simple suggestion that a window might be an idea to use.{{sfn|Anon.|2001}} When, at a preview screening, Stockhausen saw the film, which shows a madwoman writing letters from a bleak asylum cell, he was moved to tears. The Brothers Quay were astonished to learn that his mother had been "imprisoned by the Nazis in an asylum, where she later died. ... This was a very moving moment for us as well, especially because we had made the film without knowing any of this".{{sfn|Aita|2001}}

===2003–2007===
[[File:Stockhausen+Antonio.jpg|thumb|Stockhausen and Antonio Pérez Abellán during a recording session in 2007 for ''Natürliche Dauern'', the Third Hour of ''Klang'']]
{{Main|Klang (Stockhausen)}}
After completing ''Licht'', Stockhausen embarked on a new cycle of compositions based on the hours of the day, ''[[Klang (Stockhausen)|Klang]]'' ("Sound"). Twenty-one of these pieces were completed before Stockhausen's death.{{sfn|Stockhausen-Verlag|2010|loc=49–50}} The first four works from this cycle are First Hour: ''Himmelfahrt'' (Ascension), for organ or synthesizer, soprano and tenor (2004–2005); Second Hour: ''Freude'' (Joy) for two harps (2005); Third Hour: ''Natürliche Dauern'' (Natural Durations) for piano (2005–2006); and Fourth Hour: ''Himmels-Tür'' (Heaven's Door) for a percussionist and a little girl (2005).{{sfn|Stockhausen-Verlag|2010|loc=49}} The Fifth Hour, ''Harmonien'' (Harmonies), is a solo in three versions for flute, bass clarinet, and trumpet (2006).{{sfn|Stockhausen-Verlag|2010|loc=49}} The Sixth through Twelfth hours are chamber-music works based on the material from the Fifth Hour.{{sfn|Stockhausen-Verlag|2010|loc=49}} The Thirteenth Hour, ''[[Cosmic Pulses]]'', is an electronic work made by superimposing 24 layers of sound, each having its own spatial motion, among eight loudspeakers placed around the concert hall.{{sfn|Stockhausen|2007a}} Hours 14 through 21 are solo pieces for bass voice, baritone voice, basset-horn, horn, tenor voice, soprano voice, soprano saxophone, and flute, respectively, each with electronic accompaniment of a different set of three layers from ''[[Cosmic Pulses]]''.{{sfn|Stockhausen-Verlag|2010|loc=50}} The twenty-one completed pieces were first performed together as a cycle at the Festival MusikTriennale Köln on 8–9 May 2010, in 176 individual concerts.{{sfn|Gimpel|2010}}