Hi Chris,
I read an old post (2008) from you here on SOTW descibing a low E Conn Bass Clarinet. I just got one of these and would like to share with you some aspects of the instrument, particularly regarding the two speaker keys mechanism. The insturment seems to be pretty much the same as the one you describe. There are two speakers keys on the back, just above the thumb plate. But none of them are in the standard position, like in a soprano clarinet. The keys are kind of symmetrical in respect of the thumb plate (both are reachable with my left thumb) but one is a little bit on the left and the other keys is a little bit on the right. The left key when pressed opens a small hole in the upper part of the upperjoint while the left key open a small hole on the neck of the instrument.
I'm not sure how to use these keys. I can now play the lower register of the instrument (from low E to A) but the upper register is a mistery for me. I don't know wich key I should press.
continues..