You might be using too tight an embouchure, not have enough mouthpiece in your mouth or not be using enough breath support - most likely it is a combinstion of all 3.

What do you define as upper register Below Thumb and register C? or above that? if you mean above that you cannot use regular clarinet fingerings you need to incorporate half hole technique when you want to play above thumb and register C. if you mean below that you need to make sure your first finger hole is completely covered...or some sounds may not come out...or just check your horn over...a leak can be very difficult to find and cause a whole section of your range to not work...it sucks..but it happens...it could very well be your instrument or your technique

I've been playing bass clarinet as my concert instrument for 3 years and am just now mastering high notes. press down, blow alooot more air and open you throat like your sticking a basketball in there. its a fell sorta thing.

i've played in my state honor bands and orchestras and even the band of america honor band on bass clarinet.

to start off, you have to make sure the set-up of your reed and mouthpiece are all okay. if your instrument has any leaks, you're going to have trouble with upper notes.

when you play in the upper register, it's important to keep your mouth relaxed and make sure you're blowing warm air.

Recently I purchased a used Vito ResoTone bass clarinet in excellent condition. The finger spacing is awkward compared to the standard Bb clarinet. The thumb rest seems to be about 1-1.5" too low on the body of the instrument as compared to a standard Bb clarinet. In its' present position it is useless for my purposes. Do you recommend relocating it? Are there adjustable thumb rests available? (I am working with it, and love the sound)
Thanks, BobHar

Hello BobHar. I,too, have a Vito bass. I don't think you need to change the position of the thumb rest unless you want to play standing up with a neck strap. When I play sitting, using the floor peg, I place my thumb on top of the thumb rest. Try it.

Thanks for the reply. That is exactly what I am doing. I may eventually take it to a shop and have it repositioned. When playing mid G, A, B, Bb I need something to hold on to something to keep the horn from floating around.
I can not believe that Vito would place the thumb rest in such a strange location. I've played many differt clarinets and all the various type of saxes over the years and always the thumb rests were never a problem.
Regards

I started playing the Bass Clarinet four months ago. I recommend getting a 2 and a half Vandoren reed. With that reed, I can play notes all the way up to C above the staff. Of course, make sure that you embrochoure is correct and that no air is leaking from either side of your reed.

Interesting. Keep them coming. Just purchased "Essential Elements" Book 1, and am ordering Book 2. Interesting method of teaching. I learned to play clarinet from the H Klose teaching book (first published 1898) I still have the book.