Expression

Expression reed organ stop: 1. in the orgue expressif of Gabriel Joseph Grenié, expression was obtained by compressing air in the reservoir by means of a treadle; 2. in the harmoniums of the 1840's expression in form of crescendo and decrescendo was obtained by a valve that communicated variable pressure directly to the reeds without intermediary of an air reservoir. It was controlled by a treadle. This form of expression was the invention of Victor Mustel of Paris, 1843. Probably the most pop…