In the early 1990s British guitarist and improvisor Derek Bailey presented a television documentary on the role of improvisation in music. During the series Bailey visits a church on the Isle of Lewis in Scotland where we hear the unusual tradition of Gaelic psalm-singing. This kind of swarming choral effect reminds me of the singing documented on the 1989 album Polyphonies Vocales des Aborigenes de Taiwan. Other references might be Louis Sarno's recordings of the Bayaka People of the Central African Republic as well as Alan Lomax's extensive recordings of prison and work-song in America.
Inspired by these kind of choral textures The Ecstatic Lament for Jerusalem  is a plunderphonic reworking of the famous hymn Jerusalem, which is sung at the Proms every year in the Royal Albert Hall. Using realtime sampling, melodic intervals are stretched, re-ordered and repeated to create an ever increasing rapture of sound and emotion.