Drummer Ágúst left the band after the recording of Ágætis byrjun and was replaced by Orri Páll Dýrason. In 2002, their highly anticipated follow-up album ( ) was released. Upon release all tracks on the album were untitled, though the band later published song names on their website. All of the lyrics on ( ) are sung in Vonlenska, also known as Hopelandic, a constructed language of nonsense syllables which resembles the phonology of the Icelandic language. It has also been said that the listener is supposed to interpret their own meanings of the lyrics which can then be written in the blank pages in the album booklet.
Sigur Rós joined Radiohead in October 2003, to compose music for Merce Cunningham's dance piece Split Sides; Sigur Rós’s three tracks were named Ba Ba Ti Ki Di Do, and released in March 2004, while Radiohead's contribution was never released. Sigur Rós' 1997 debut album Von found a U.S. and U.K. release in October 2004.