Tuning rings, cor anglais: Mollenhauer/Buffet - 2-6mm

Every cor anglais player is familiar with the problem:

You have to play in a cold church and the cor anglais is much too high. So you quickly pull out the bocal a little bit and it's perfect - almost. So you pull it out a little more. Suddenly the cor anglais is transformed. The intonation is altogether lower, but individual notes aren't in tune with each other anymore. Certain notes are muffled and the attack feels strange.

The reason for this is the hollow space that is created between the end of the bocal and the top of the cor anglais insert. This hollow space is wider than the bocal itself, causing the issues mentioned above.

This is where the tuning rings come into play, as they, in a way, extend the bocal by 2-6mm. As a result, the cor anglais is altogether lower but absolutely in tune with itself.

2mm height in tuning ring corresponds to roughly 1,5Hz change in pitch.