The album, as previously reported, features songs written for artists that didn't necessarily make the grade. Sia's written for a tonne of artists, but not everything's been used - this is a collection of songs meant for Beyoncé, Rihanna, and others, that, clearly, were too good to mothball.

This Is Acting will be released 29 January. Check out her Instagram page to see the meticulous announcement.

As well as "Bird Set Free", the album will feature "Alive", a co-write with Tobias Jesso Jr. and Adele.

Listen to "Bird Set Free" below.