CD, limited edition of 150 copies. One piece, twenty-seven and a half minutes. A German and an American, a generation and an ocean apart, who had each spent decades on the sustained tone and had never recorded together until now.

Werner Durand has played his own music for saxophones, Iranian ney and self-made wind instruments since the late 1970s. He studied with Ariel Kalma in Paris, Indian classical music with Kamalesh Maitra, and the ney with Ali Reza Asgharia. In the early 1980s he began building instruments out of plexiglass and PVC tubing, and those are what he plays here: instruments with no repertoire behind them, no inherited fingering and no agreed way of playing them wrongly. He formed The Thirteenth Tribe in 1990, and from 1990 to 1997 he was a member of Arnold Dreyblatt's Orchestra of Excited Strings, which appears twice elsewhere in this selection.

John Krausbauer plays violin, held rather than phrased, with the bow kept moving so that the piece never stops to take a breath.

The density is not built by overdubbing. It is two people holding, and what fills the space is the harmonics that arrive on their own: an unrelenting buzzing choir, in the label's phrase, of notes that neither instrument is actually playing. That is a description of the mechanism as much as of the effect.

Reviewers have placed it next to Tony Conrad, Catherine Christer Hennix and La Monte Young, all three of whom are elsewhere in this list, and that is the right neighbourhood. The register, though, is darker than any of them. It is closer to a dirge than to a meditation, and it thickens without ever giving the usual signals that it is about to.