The physical characteristics of the building for which a particular piece of music was written must be considered an essential element in any attempt to recreate the aesthetic impact of that piece. This article is concerned with a small building in Hamburg, not one of the four main churches (Hauptkirchen) or the Cathedral, but the St Gertrude's Chapel, or Gertrudenkapelle, which acted as an important centre of musical activity in the 17th century. Because it made particular provision for the performance of polychoral music, a study of its layout and of contemporary descriptions of performances can shed light on the performance practices associated with polychoral music elsewhere in the early Baroque period. The Gertrudenkapelle was built between 1391 and 1399, as a sister church to the nearby Jacobikirche, on cemetery land owned by the St Gertrude's Guild (see illus. 1).' The function of this body was to provide housing, health care and burial assistance for the poor and the sick (especially lepers); it was aided in this by