"The Lonesome Traveller" covered Sigur Rós songs acoustically in an alt-country style.

Kjartan also contributes to Sigur Rós's orchestral and string arrangements, along with the group Amiina.

On 16 November 2010 Kjartan Sveinsson performed in The Whitelight Festival, along with Jonsi & Alex and The Hilliard Ensemble.

"[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.

[9] On 14 February 2022, Sigur Rós made a social media post announcing Kjartan was returning to the band [10]