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This kind of double pipe is based on a number of prototype instruments. The only medieval double pipe of the flue kind has been found in Oxford, England, and while it is in unplayable condition, enough remains to have a good idea of what it was like.* Other similar instruments exist in the form of folk pipes used in the South of Italy, and there are double flue-type pipes used in the Balkans, from Slovenia to Greece. All of these have variable fingerholes. The launeddas, the national instrument of Sardinia, are reedpipes, but have the same type of fingering pattern, as do the chanters of the South Italian zampogna and chiaramella bagpipes. This broad type of double pipes with both pipes fingered, and therefore polyphonic music playable on them (within limits) existed from truly ancient times. Some of the earliest instruments discovered in Mesopotamia and Egypt are of this type, as are the Greek aulos. All known ancient double pipes are reedpipes, but in mediaeval times flue pipes also were made with this type of fingering, as is clear from contemporary illustrations as well as the only surviving instrument.
Click the image below to find a selection of sheet music for pieces from various periods arranged for the double recorder in PDF format.
Bob Marvin: A double recorder
FOMRHI quaterly 31 (1983) comm. 453
1 Rata (Metrosideros Robusta) is a native New Zealand tree. According to some handbooks the second heaviest timber in the world. While difficult to dry, once dry it is very stable. The wood is very dense and smooth, but not particularly showy
All sound samples played by the maker, unless otherwise specified