So I have been starting to focus on my mouthpiece buzzing to work out some inconsistencies on some partials.

Through my exercises I can buzz virtually as high as I want, up to the high Eb's and F's and such, but when I try to buzz through my low register I can't buzz lower than an in staff C (C3 I believe). I can play through my trigger register and my lower partials, but they are more a weakness than a strength.

Are there any exercises that can help me develop into my low range buzzing? Or is this possibly a larger embouchure problem? My high range really excels, but this is just a major problem I have now.

I have a hard time buzzing low notes on a mouthpiece, but no issue whatsoever playing them with a full instrument. I think it comes down to back pressure.

If I practice buzzing and have the need to go lower I buzz through a leadpipe or cover a bit of the end of the mouthpiece with my finger. After a bit of buzzing with some help of that back pressure I can buzz lower without it. I haven’t noticed any change in how my lower register playing that I couldn’t also attribute to the rest of my practice routine, though.

I can buzz down to low C ish. Down a 4th from a couple months ago! That's all from having a better setup and not trying to "control" too much with the face down there. All air and a relaxed aperture.

Low buzz seems to be a matter of getting more mass involved in the vibration. Pouting, pushing forward in a pursed lips way, pulling corners way in, something like that.

Try taking off the outer slide and buzzing through the upper inner slide. It won't want to go any higher than about D in the staff, but that's OK. Start there and go gradually down. As that gets easier, use a spare leadpipe and/or a flexible plastic tube from the hardware store (1/2" diameter works well for large shank). The longer the tube, the more helpful resistance you'll experience in the low register (and the lower your upper register cutoff will be). I find 4-1/2" or so is about as short as still makes a difference.

I find mouthpiece work with a tube helps keep me from getting overly tense and pinching the sound. Keep the sound rich, full, and a even a little foggy/airy when you play only the mouthpiece, not buzzy.

I also find that many players seem to have the instinct to tilt the mouthpiece up and their head down when they approach the low register. For most (but not all) embouchures, this is the opposite of what is helpful. Try keeping your head straight and letting the mouthpiece tilt down as you go lower, anchoring on the lower lip and allowing the upper lip to vibrate.

<YOUTUBE id="RB9vJpNYuL0">https://www.youtube.com/watch?v=RB9vJpNYuL0</YOUTUBE>

<YOUTUBE id="tIkdTTX-UEI">https://www.youtube.com/watch?v=tIkdTTX-UEI</YOUTUBE>

I think the OP have left us, the thread is geting old. But with all respect Gabel, I have seen so many good basstrombonists, not just a few, who tilt the horn up for low tones. If it sound good (and it very often does) it is good.