C2-D2. Christlieb, Don. Pictoral Fingerings for Bassoon. Published by author, 1966, p. 19. Timm, Everett LeRoy. The Woodwinds; Performance and Instructional Techniques. Boston: Allyn and Bacon, 1964, p. 171. "Prepare a wedge of wood, cork, plastic or cardboard."

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C-tr D-wedged

Heckel-System (German) Bassoon Trills and Shakes by Note Names