Checking a Bassoon for Air-tightness
For a bassoon to work properly, especially to control quiet, low notes, the instrument must be as air-tight as possible. It should be tested joint by joint every month or so or if things don't feel 'quite right'. Players often spend ages struggling to get a reed to work when the problem is actually a leaky instrument.
1) The crook (bocal): test this by putting a finger or thumb over the wide end and also (with a clean finger) closing the 'pin hole'. Then suck out some air and close it off with your tongue. This vacuum should hold for several minutes. There's not usually a problem, but occasionally, a crook can develop a split along the seam that is made in the construction process. If this happens, seal it up with some sellotape until you can get it to a good repairman (this is not a job for a cowboy).
2) The tenor joint: put a finger over the narrow end of the tenor joint, close the finger holes and suck air out from the wider end. If you can hold a vacuum for 90 seconds, that is extremely good and we should be aiming for this (you might even need to wet your fingers to hold the vacuum this long). 20 - 30 seconds is still good while most instruments only manage about 10 seconds. If it is much less than 10 seconds it must be improved.
3) The butt joint: close all the holes by fingering a low E and seal up the wide end with your cheek and suck air out from the narrow end. If you have a beard, you'll have to remove the U-bend and test each half separately (or shave your beard off!). A 30 second vacuum is excellent and anything less than 10 seconds should be sorted out.
4) The long joint: roll up your trouser leg press the low B key down and close the wide end with your calf and suck through the narrow end. 15 seconds is fine and anything less than 10 seconds, again, should be sorted out.
5) The bell joint: as above or use the palm of your hand to close the end.
With all except the tenor joint, the length of time for holding a vacuum is measured by taking off the fingers that hold down keys that are normally open and waiting for them to pop open.
6) The cork connections between the joints and the linkages between the joints: to test these put the whole instrument together and get a friend to cover the end of the bell joint with the palm of his or her hand.
