C#6. Wangler, Steven. In Apfelstadt, Marc and Klimko, Ronald. Bassoon Performance Practice, Teaching Materials, Techniques and Methods. Idaho: University of Idaho, 1993, p. 73. "Both Ab keys (fingering won't work if the two Ab keys open the same hole). Bite and feel the harmonic.
x o o | o o o Ab a Ab
Psalmi CL: VI Omnis spiritus laudet Dominum. Alleluia.