Flow acoustical determinants of historic flue organ pipe voicing practices
Dirk Steenbrugge · 2010
Pipe organs sound differently depending on the regional and contemporary circumstances of their genesis. In order to adequately conserve them it is important, due to the scarcity of sources provi ding direct information on the building process and particularly on pipe voicing practices, to be able to specify as much as possible the factors that determine their sound signature. To this purpose an organized overview of some of these practices is proposed as a starting framework, exposed with reference to the classical flow-a coustical flue pipe models developed by, among others, Cremer & Ising, Coltman, Elder and Fletcher. On the other hand, a method is presented to assess the tonal and musical effects of voicing configurations, using a 'voicing jack'-like system featuring a complete stop rank of experimental pipes with electronically controlled, continuously variable flue, mouth and toe hole geometry. On this playable system the voicing (and tuning) of the pipes can be varied easily, rapidly, precisely and reversibly. In order to characterize spe cific voicing strategies both approaches are combined by relating the musical significance associated with the test voicing configura tions to corresponding values of a set of characteristic dimensionless ratios. Well-known voicing methods like open or closed toe and over- or underblown voicing are identified accordingly, as well as less common or builder specific procedures.