"The photo you have
posted of the Stubbins SK middle Bb mechanism is actually of the
mechanism used on the Selmer Omega model in the mid-50s. The
switch between the register vent and the Bb vent is controlled by
the thumb ring. If the thumb is off the ring, a strong spring
opens the lower hole for Bb. When the thumb is on the ring, a
lever attached to the ring holds the Bb key down and the weakly
sprung register vent can open.
The Stubbins SK instruments
and photos I have seen were activated by a lever attached to the
A key, not the thumb ring. Also, I believe the Bb vent was
positioned more toward the right side (viewing the instrument
from the back) so the thumb-touch lever didn't arch over the
Bb hole.
I played Selmer Omegas for
several years. The Bb was beautiful, but the mechanism was not
reliable. The balance between the strong and weak springs
constantly got out of adjustment, and the register vent (which
was opened only by the weak spring) tended to stick closed.
Selmer even provided little slips of sandpaper to remove the
crud. Also, to get the Bb, your thumb had to be all the way off
the ring. The Bb key went up and down with the thumb ring, and if
it wasn't all the way open, the register vent would open
slightly, spoiling the note. This meant a lot of thumb movement
and was a problem in passages going back and forth between Bb and
the adjoining C (as in the Debussy Premiere Rapsodie).
This was not a problem with
the Stubbins SK, since the A key is always all the way open to
play Bb. However, the problem with opposing springs remained,
which I think is why it hasn't been adopted.
A number of years ago, there
was a letter in, I think, The Clarinet from a major symphony
player (I don't remember which one), saying that he had
gotten an instrument with a special Bb mechanism and proudly
brought it out for the solo in Debussy's Prelude to the
Afternoon of a Faun, which has a long, exposed Bb. The conductor
(Ormandy?) immediately stopped the orchestra and demanded that
the player go back to the unimproved fingering, which he said was
what Debussy had in mind. So it goes."
"Mr. Shaw correctly
identified the photo as being a Bb-register mechanism made by
Selmer. I would like to add the following information to what he
said:
The Selmer mechanism was an
either/or mechanism not unlike what is used on their Bundy (now
Selmer USA), plastic bodied bass clarinets. The Bb tone hole is
an acoustically correct tone hole for Bb. Notice in the photo
that the Bb key which resides under the camel humping register
key is radially around the body from the side or trill Bb key
(jumper key #3). With this mechanism, only one key opened at a
time, either the register key or the Bb.
The Stubbins SK mechanism
was different. On this mechanism, the lower hole (which was also
in a similar place as on the Selmer -- under a camel humping
register key) opened along with the register key to produce Bb.
This key was a supplemental vent used in conjunction with the
register key for the production of a better sounding Bb.
A third type of mechanism
designed to improve upon the compromised Bb/register key dilemma
was the Mazzeo mechanism. This mechanism was an articulation of
the Bb jumper key that was actuated by the bottom ring key of the
upper joint. The ring key of the lower joint (because of its
connection to the upper joint) would also activate and open the
articulated side Bb key. Producing Bb then became a matter of
playing throat tone A and closing either of the rings below the
first ring key. The Bb key was overridden and closed by the left
them closing the thumb hole. The thumb hole, by the way, was not
an open ring key on the Mazzeo model clarinets, but a key with a
pad.
One of the great
shortcomings of the Mazzeo mechanism was that any and all
resonance fingerings for throat tones became impossible simply
because any fingers that were put down opened the articulated
side Bb key. Also when descending to throat tone A, all other
fingers had to quickly and cleanly open or a Bb blip was
experienced.
