I've known the music of Ms Pook for many a year. She appears regularly in film and theatre, inluding Gangs of New York and Jarman's Edward II. She won an Olivier this year for the sound design of St Joan at the National Theatre.
The Masked Ball is from her album Flood - it's well worth getting if you like ethereal music. Likewise the album Untold Things.
Not exactly the same but full of wild and evocative vocals is Flamma Flamma (Fire Requiem) by Flemish composer Nicholas Lens. There are some sound samples at Amazon - A truly amazing requiem!