I think I understand what your teacher called "rounded". I noted that you have a bit of a "smily" embouchure. I would advise you to try a more relaxed one. Use the center portion of your up lip to control the amount of air and the direction of the airstream.
Although youtube is not as good as it should be to give a clear idea of your tone, it seemed you have good tuning and your tone did not seem to be unadequate to this peace.
It's natural some "buzzing" when playing the flute, because our sound is produced by an airstream whose part of if goes outside the instrument, just the contrary of all other wind instruments. What you have to keep in mind is that you need control not to let it exagerate the buzzing sound.

Other thing. I would play this peace far slower than it appears at the recording you sent. Really seemed like the player is in a rush. I don't know if it's because of some sort of compression that youtube does, but I didn't like the velocity of this interpretation.

I think you already have much better tone quality than the other "younger" flutists who post their videos here. I think that your tone quality is suitable for a Mozart concerto.

Other things to consider: How large is the orchestra for the concerto contest? What are the acoustics of the hall/venue? Sometimes we can't be sure of the exact sound that we want until we're sure of all the variables involved in the actual performance.

This is so true!

Still about the fact that I dislike the speed of the recording, you may think about this particular 2o movement as if you were a singer. You must feel your flute is singing, just like a singer would do an aria in an opera.
That's why Mozart's concertos are always chosen in contests like this. They just put all your skills in evidence. Technic is basic, but expression is something unique to your experience and gift.

theflutist94, when I listened to the recording of you playing I was intrigued and captivated by the sweetness and singing quality of your tone and smoothness while playing. I am not the best to give advice as I tend to do my own thing and not always play it by the book. Good luck!

I just went and watched a bunch of your videos. I am in love with your work I like that you have perfect pitch. That is my biggest pet peeve when anything is off. I have a super sensitive ear. Lady Gaga on flute was fun to listen too also.

In addition: Any advice on what kind of vibrato to use? My teacher said to use a more narrow but fast vibrato rather than a wide one, so the piece won't sound heavy.

I was just waiting for you to ask about it... :-)

Vibrato is quite a controversial matter. But IMHO you should not abuse that in a Mozart concerto. Do narrower is a way you can make it softer, but in terms of the velocity of vibrato (the frequency of vibrations) each flutist develop his/her own. I think your vibrato is beautiful the way it is, nothing should be changed by now. Just remember never to exagerate, so the peace does not become romantic. Keep the phrases cristal clear, almost thinking as it was a baroque peace, like one of the wonderful slow movements from Bach's Sonatas.

very nice tone and vibrato, let the vibrato being something added to your tone, otherwise it gets in the way..if you could relax the corners of your embouchure you will have more flexibility to attain more color in your tone

Hey, what happened to this thread?

Hey everyone, it's me again...I think the account I used to post this thread got deleted for some odd reason? I bet it's because I posted that link to one of my videos on YouTube. Weird! Well here's my new account!

I just wanted to say thank you to everyone for the advice - it's been helping lots! I appreciate it. And thank you for the nice compliments, Kate, they mean a lot to me.

You are welcome I look forward to more of your vids.