This is very hot off the presses coming as it does from the 24 Feb Introducing Mixtape.
On their soundcloud page this song is simply tagged ‘ethereal’. That same page introduces them thus:
Liverpool band Bird is the creation of Adele Emmas, Sian Williams, Christian Sandford and Alexis Samata. Together they create dark, haunting, atmospheric music. With beautiful, siren-esque vocals, tribal, hypnotic drum beats and spellbinding guitar work
The band seemed familiar, and sure enough, the very last entry on the 2012 Introducing Mixtape page is this, with my comment ‘distinctive and unusual female vocal’
Link to band’s site.