The important thing about this extension is that it does not effect the intonation of your instrument. Using a cardboard or plastic tube to lengthen the bassoon is a nice and cheap way to do it, but other notes (surprisingly some of the ones in the staff) tend to go flat.
This extension is not something that you stick in the end of your bassoon. Instead this “Bb bell extension” is a small piece which goes in-between the bass joint and the bell. It effectively makes the bassoon a few inches longer and lets you play low A.
A video that shows a little bit about how I made the extension and demonstrates how it works.
The best part is that you play everything normally, but to play low A all you have to do is turn the extension 90 degrees and it changes whether you’ll play Bb or A.
I made my extension using a pretty cheap but broken bassoon that had approximately the same color as my Fox.
The next thing I did was saw the bell of the “donor” bassoon down to 8 inches in length. Next, I got the help of a friend who’s got a really nice woodshop who carefully turned “donor” bell on a lathe so that my normal bell would fit on the end.
Note: The inside diameter of a bassoon actually varies a LOT from one manufacturer to another. This means that its not possible to make bell extension that will work on every bassoon. They have to be done carefully one at a time. So, I did a lot ofsanding and eventually the extension fit onto the bass joint of my bassoon and the bell fit on the top.
With the woodworking done, I fabricated a new metal key to make it all work. The extra key closes the pad on the extension as well as the one above on the bell.
A huge thank you to John at www.neil-woodworking.com for helping with this project!