I used to play a lot of contrabassoon. Since leaving the university system I don’t really have regular access but I make a good reed and played pretty well at a time.
Contrabassoon has some odd fingering issues. I compiled a fingering chart from Susan Nigro and Roger Soren (who play on very different contras, but they share some consistencies). Hard to find good fingering charts for contra, so I’ll put this one out there. Hopefully my nomenclature is helpful. “a” is the first/lower vent, “d” is the upper vent. Everything else is consistent from bassoon keys.
Trent Jacobs, bassoonist 
Charles Gaskell
/ April 27, 2014I’m interested that or the fingering for F below middle C, you give “seven fingers down”, rather than “all fingers off” – is there a reason for this, or does it depend on whether you are going E-F-E or G(b)-F-G(b)? What do you do about E-F#-E?
Trent
/ April 27, 2014On many contrabassoons the open F is quite flat and not terribly resonant. The harmonic fingering given is almost always more resonant and in tune. Of course your contrabassoon may have a perfectly fine open F, but many consider this the “full” fingering on the contra.
But you are also right about technical considerations, the long F is handy for F to G or Gb, but the open F is often better for passages that don’t go any higher.
hdtube
/ November 21, 2019I have recently started playing a Mollenhauer contrabassoon I have some problems regarding the high notes from high Bb to high D as I cannot find any fingering charts that would describe the fingerings Can anyone help me please?
Trent
/ November 21, 2019Richard Bobo has a fingering chart that will likely help you. I’m pretty sure he plays a Mollenhauer: http://me.subcontrabassoon.com/BoboCbsn1.pdf