(b ?Scotland, late 10th century; d Cologne, 18 Nov 1052). Benedictine abbot and theorist. As abbot of St Martin at Cologne, he decreed that his monks should sing the Office of St Gregory the Great composed by Pope Leo IX (1049-54) instead of the Common of Confessors. He wrote three treatises, dealing with singing, the Gregorian psalm tones and consonances.




