Bass Clarinet Adaptive Left-Hand Modification

This bass clarinet belongs to a young man who lost the use of his third and fourth fingers on his left hand. That meant he lost the use of several keys, namely the G/C (third finger plate), Inline Bb/Eb, G#/C#, and the left hand pinky table. With the help of the engineering department at his college, he actually designed mechanisms to reassign most of those keys to his left thumb, and 3D printed a plastic prototype that was somewhat functional. Plastic is too flimsy to make the necessary linkages, though, so he came to have a more rigid version made from nickel and permanently installed. As we explored the possibility of doing that, it quickly became clear that the prototype, while based on some good ideas, wasn't as efficient as it could be because it didn't prioritize the most frequently used keys, didn't allow for smooth movement from one key to another, and didn't provide natural-feeling fingerings that would be easy to learn. It also put all the work on the left thumb, which already has two keys to operate. Finally, and this may seem like a small thing, it didn't fit in the case with the extra parts configured as they were. With the help of Brian Russell, with whom I collaborated on the one-handed saxophone, we designed a whole new set of mechanisms that distributed the workload to the left hand second finger and right thumb, while making the most important keys easiest to reach and actuate. The new system also fulfills a few of the critical design principles for woodwind keywork:

1) It should be possible to move from any note to any adjacent note by only lifting or putting down fingers. It should not be necessary to move any finger from one key to another. Where that is necessary, it should be possible to "slide" the finger from one key to the other without lifting. For instance, the low keys on a saxophone have rollers to facilitate such sliding.

The original design required the thumb to operate 5 different touchpieces: G/C, G#/C#, Bb/Eb (the small inline key), the regular thumb key, and the register key. There were no alternate fingerings for G/C or G#/C#, so the only way to play those notes was with the thumb, and moving between them would require lifting and moving the thumb, which makes legato playing all but impossible. We created new touchpieces and added alternate touchpieces to allow movement between any two adjacent notes without having to lift and move any fingers; there’s always a way to move smoothly through any close interval, with two exceptions (see below). The only place where a finger might have to move is the left hand middle finger, which now operates both A/D and G/C, so we created a hinged tilting connection between those two touchpieces, which facilitates a smooth slide from one to the other. Even so, there is an alternate fingering for G/C that would allow those notes to be played without moving the middle finger.

2) Generally, depressing more mainline keys should lower the instrument's pitch, so that traveling "down" the instrument body with your fingers also brings down the pitch. 

We achieved this, which hadn't been part of the original, thumb-heavy design, by placing the G/C plate below the A/D plate, where one would naturally expect it to be. The alternate fingerings, which are outside the mainline, don’t completely adhere to this principle, but that’s true of alternate fingerings on any woodwind instrument, which have to be “fit in” to the mechanism wherever there’s space and an available finger.

3) Nearby keys should have a uniform amount of travel, that is, the distance a key moves between its fully open and fully closed positions. 
This one took some doing because travel is heavily reliant on the distance of a touchpiece and pad from the axis around which the key pivots. Where the touchpiece and pad are mounted separately on a key, if the touchpiece is further from the axis it will need to travel further than the pad, and vice versa. Uniform travel has a lot of influence on the “feel” of an instrument. I’ll admit there are places where the travel is a little more or less than in other places. I needed to build touchpieces around existing mechanisms, which meant sometimes placing them further from the axis than would have been ideal. The F/C touchpiece for the right thumb has noticeably more travel than other keys, because it wraps around the body and is pretty far from the axis. But because that thumb only operates one other touchpiece (the new G#/C#), and because it would have been prohibitively expensive to add intermediate mechanisms that would have reduced the travel, the abnormal travel is a reasonable trade-off to have the use of that key. In the original design, that key wasn’t included because it’s an alternate fingering (the primary being with the right hand pinky), but it’s a very useful alternate fingering so having it feel a little “off” was better than not having it at all.

A few keys just couldn’t be accomodated in the new mechanism and were, for lack of a better term, abandoned. They are all alternate fingerings, so those notes can still be played: The inline Bb/Eb (there are three other fingerings for these notes with the addition of a saxophone-style “bis” key for the left hand middle finger), the left hand F#/C# and the left hand E/B. As eluded to above, these are the two fingerings that it’s not possible to move between without lifting and moving a finger, because after the loss of these toucphieces they can both only be played with the right hand pinky. The same goes for moving between either of those fingerings and Ab/Eb, which is played with the same finger. It would be possible to add them to the right hand thumb, as was done with F/C, but the expense of doing so went well beyond the budget for this project.

The owner wanted to preserve the instrument in such a way that it would be possible to return it to a “standard” configuration. That meant I couldn’t modify or cannibalize any of the existing keywork, as it will be set aside. Fortunately, this is a relatively new Yamaha instrument, so getting replacement keys to modify was fairly easy and cost-effective, far less expensive than making everything from scratch. I used as much of the material from those keys as possible, cutting and splicing where needed. The thumb rest, which has a large plate for the thumb to sit on (making it easier to move to the new right hand thumb keys) is from a Buffet Prestige bass clarinet, an instrument that has multiple thumb touchpieces. The alternate G/C and G#/C# touchpieces are from the Low B and Bb keys on a Fox bassoon. The narrow thumb touchpiece and roller are from a Yamaha 621 bass clarinet. The posts for the new G#/C# thumb mechanism were taken from another Yamaha 221 bass clarinet. All the other touchpieces, arms, screws, etc. were hand made from nickel silver stock. I really had to practice my brazing skills before taking this on, as there were a lot of joints to braze. There is one soft-soldered joint, where the new A/D touchpiece is attached on top of the old one. The heavy mass of those parts and the large size of the joint would have required a huge amount of heat to braze, and I wasn’t confident I could do that without melting the parts. But because the joint is so large, silver bearing solder is plenty strong enough to hold it together.
And guess what? It still fits in the case, and is pretty easy to take apart and put together, since there's just one extra bridge between the joints (for the G#/C#).

The pictures below show the new mechanisms, but the best way to understand this instrument is to view the fingering chart, and especially to study the trill fingering chart to see how these new touchpieces facilitate movement between adjacent notes. They can be viewed here: Fingering chart, Trill fingering chart

The front of the instrument, showing the new touchpieces for the left hand middle finger and right hand index finger. The hinge between the A/D and G/C touches allows the player to slide from one to the other. Also visible on the right side of the image is the small Inline Bb/Eb key, which has had its touchpiece removed to make room for the new mechanism. That key wouldn’t have been usable anyway, since it's activated by the 3rd finger, which the player can’t use. But in order to replace that alternate fingering, the “bis” key was added.
At the bottom of the picture are the alternate G/C and G#/C# touchpieces, which are actuated with the right hand index finger.

A close-up view of the A/D and G/C touchpieces, at the left of the picture. The touchpieces are hinged together, and the head of the screw that serves as the hinge is visible. A light leaf spring runs under the G/C touchpiece and holds it to the adjustment bar, to prevent it from flopping around. The adjustment bar has two screws that for regulating the closure of the pads and adjusting the feel so there's no "slop" in the mechanism.
Visible in the center of the picture is the remnant of the arm from the Inline Bb/Eb key, which had to be removed to make room for the new mechanism.

The top view of the A/D and G/C touchpieces, showing the hinge. Also visible is one of the adjustment screws mentioned in the previous image. The other screw is under the G/C touchpiece and not visible. At the top of the picture you can see the Bb/Eb "bis" key extension.
It's also clear from this image how the arm from the original Bb/Eb key would have interefered with the new mechanism, and why it had to be removed.

 A view of the back of the instrument, showing the new thumb rest with plate, and the alternate G#/C# and F/C touchpiece. Also visible is the rocker mechanism that connects the G#/C# touchpiece to the key on the upper joint.

From the side of the lower joint, showing the long arm that connects the F/C lever with the thumb touchpiece. The left hand E/B and F#/C# touchpiceces had to be removed to make room for that arm, and are set aside with the rest of the original keys. I left the screws in place because they're less likely to get lost that way!

A view from the other side of the lower joint, showing the rocker that links the new G#/C# thumb touchpiece to the G#/C# key on the upper joint.

The alternate G/C (left) and G#/C# touchpieces. The G/C moves independently, but pressing the G#/C# will also actuate the G/C. When playing G#/C#, the G/C pad must be closed, and this mechanism accomplishes that. Closer to the top of the image, you can see that the arm of G#/C# passes under the arm of the G/C, which was necessary to configure the keys this way. It was also a very challenging bit of engineering, at least for an amateur designer like me.
It's not clearly visible here, but I also had to file a notch in the G#/C# arm, so that the screw for the G/C key can be removed when disassembling the mechanism for service. The arm is right in the path of that screw. That was a problem I hadn't thought about, but thankfully was able to catch before brazing the arms together.