Editing Karlheinz Stockhausen (section)

===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}}