Barker collaborated with musician KK in 2004 to release Lullaby, an album of night-time songs for children. That same year, she appeared as a backing vocalist on Sia Furler's album Colour the Small One, appearing on the track "Natale's Song". She followed this with a solo album entitled Earthbound, released in 2005. Barker has also worked with The Egg ("Walking Away"), electronica artists Grooverider ("Time and Space"), Groove Armada ("Inside My Mind (Blue Skies)" and "Your Song") and the acid-jazz duo Muki ("I Don't Want to Know"). Barker was featured in a 2006 British Airways UK television campaign, singing a cover version of John Denver's "Leaving on a Jet Plane". Barker also featured as a guest singer on Quiet Letters by Bliss, and then collaborated and provided vocals for their album entitled No One Built This Moment.
