|Born||2 January 1978|
|Instruments||Piano, keyboards, organ, flute, tin whistle, oboe, banjo, guitar, bass guitar, vocals|
|Associated acts||Sigur Rós|
Kjartan "Kjarri" Sveinsson (Icelandic pronunciation: [ˈcʰar̥tan ˈsveinsɔn]; born 2 January 1978) is former keyboardist for the Icelandic post-rock band Sigur Rós. He joined the band in 1998. A multi-instrumentalist, he has also played such instruments as the flute, tin whistle, oboe and even the banjo, as well as many of the unorthodox instruments that contribute to Sigur Rós's distinctive sound. He also plays the guitar.
Kjartan has performed under the pseudonym "The Lonesome Traveller" with Sigur Rós band-mate Orri Páll Dýrason and Amiina violinist María Huld Markan Sigfúsdóttir (whom Kjartan married in 2001). "The Lonesome Traveller" covered Sigur Rós songs acoustically in an alt-country style.
Kjartan also composed scores for the 2005 Academy Award nominated short film Síðasti bærinn (The Last Farm), for award winning director Ramin Bahrani's 2009 short film Plastic Bag which features the narration of legendary filmmaker Werner Herzog, and for the 2009 film Ondine directed by Neil Jordan. Kjartan also contributes to Sigur Rós's orchestral and string arrangements, along with the group Amiina. He is also featured heavily on The Album Leaf's album, In a Safe Place, playing a wide variety of instruments.
Kjartan is a member of the advisory board for Kraumur Music Fund, which aims to "strengthen Icelandic musical life, primarily by supporting young musicians in performing and presenting their works."
On November 16, 2010, Kjartan Sveinsson performed in The Whitelight Festival, along with Jonsi & Alex and The Hilliard Ensemble. Kjartan composed Sonnets of his own, as well as the world premiere of his new piece entitled Credo. Credo is Latin for "I believe". The performance was streamed live on NPR's website.
On 17 April 2011, Q2 - a listener-supported, New York City-based Internet stream devoted to the music of living composers - along with NPR named Kjartan Sveinsson in a list of "100 Composers Under 40".
On 19 Feb 2014, Kjartan showcased 'his most ambitious musical work' since leaving the band in the form of a collaborative theatre set-piece with Iceland's acclaimed contemporary artist, Ragnar Kjartansson. The work, titled 'Der Klang Der Offenbarung Des Göttlichen (The Explosive Sonics Of Divinity)' was performed at Berlin’s Volksbühne theatre, in cooperation with the Deutsches Filmorchester Babelsberg and the Filmchor Berlin.
In a post on Sigur Rós's Facebook page announcing an "ask me anything" Q&A session with fans via the social news website Reddit on January 24, the band referred to themselves as being a "now three-piece band."  The band confirmed Kjartan Sveinsson's departure during a Reddit Q&A session, stating that "...he has left the band. He said he spent half his life in the band and it was time to do something different." 
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