Janet Cardiff's artwork Forty Part Motet 2001 is an audio installation reworking the sixteenth-century choral work Spem in Alium by English composer Thomas Tallis.
The artist worked with the Salisbury Cathedral Choir to record 40 individual singers, playing each voice through its own corresponding speaker. The speakers are carefully positioned in eight different groups of five, responding to the structure of Tallis’s complex vocal piece, or motet. Each group forms a choir of five singers with different vocal ranges: a bass, baritone, tenor, alto and soprano.