Mirror and Tongue Position - Part 1
I was at S.P.A.H. last week (not "the spah," but S.P.A.H., www.spah.org ;-) and I found myself often working on a student's tongue position to help them fix issues with their tone. The #1 issue was they had the back of their tongue humped up, causing problems with sounding notes and generally giving them a very weak tone.
Here's how to check it for yourself.
Go in front of a mirror... close your eyes... open your mouth enough to see your tongue position once you open your eyes... drop your tongue in the back... confirm that it feels correct... open your eyes!
For the majority of people, their tongue will be humped up in the back, even though they "think" it's down in their mind's eye, where they cannot confirm its position. So... the answer is to work with that mirror for a while until you can repeat the process above and always have your tongue down.