any noats starting with C

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come out high.

You must be talking about the thumb register key here.

There are a number of reasons it doesn't close -
1. The key has been damaged
2. Likewise the pad
3. The spring that closes it is broken or become weak
4. The hinge rod has become rusty or has old gunky oil on it due to lack of maintenance.

Either way it should be an easy job for a competent technician to sort. Your teacher or band director should be able to tell you who's good in your area or might even be able to do it for you.

Good luck.

Ya, my teacher said to push on it.but I need to do it every week.