From the Bassoon-Family Fingering Companion by Terry B. Ewell - "For best quality of tone and usually fine tuning" Corey, Gerald E. "How to Improve Your Tuning on the Bassoon." The Journal of the International Double Reed Society 8 (1980): 33. Moritz, Frederick. "A Dissertation on the Use of Alternate Fingerings for Some of the High Register Notes on the Heckel and Heckel-Type Bassoons." The Double Reed 8/3 (Winter 1985): 28, 29, 32.