Kjartan has performed under the pseudonym "The Lonesome Traveller" with Sigur Rós bandmate Orri Páll Dýrason and Amiinaviolinist María Huld Markan Sigfúsdóttir (whom Kjartan married[2] in 2001). "The Lonesome Traveller" covered Sigur Rós songs acoustically in an alt-country style.[3][4]
Kjartan is a member of the advisory board for Kraumur Music Fund,[5] which aims to "strengthen Icelandic musical life, primarily by supporting young musicians in performing and presenting their works."
On 16 November 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. 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".[6]
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 24 January 2013, the band referred to themselves as being a "now three-piece band."[7] 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."[8]
On 19 February 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 Sounds of the Revelation of the Divine) was performed at Berlin’s Volksbühne theatre, in cooperation with the Deutsches Filmorchester Babelsberg and the Filmchor Berlin.
In February 2015, Kjartan Sveinsson again collaborated with Ragnar Kjartansson, being involved in a performance art exhibition at the John Curtin Gallery and the Fremantle Arts Centre in Perth, Australia.[9]
On 14 February 2022, Sigur Rós made a social media post announcing Kjartan was returning to the band [10]
^"Reddit Q&A Announcement". Sigur Rós (official page). Facebook. 23 January 2013. Archived from the original on 26 February 2022. Retrieved 23 January 2013.