Eb2-F2. 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.

"Clumsy, but in tune." Trill D and E keys together:

    Eb
x x x | x x x F
         E-tr
  D-tr

"The F is flat." Cooper p. 12.

   Eb Db
x  x  x | x x x F
     w     E-tr
     D

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