QUESTION: I had the horn out this afternoon and it sounded like the sputtering was near or in the bell, like something may be obstructing the sound. Could there be a problem with the mouthpiece? I blow into the mouthpiece and can get some lower, though clearer, notes. The sputters seem to come from the bell area. (Last night, I listened to a CD by Barry Tuckwell and it sure sounded good!)
ANSWER: Have you taken out all the slides and turned the horn around a few times to check there's not a whole lot of water anywhere?
It would be also useful to know what kind of horn and mouthpiece you are using...
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QUESTION: I just let out a lot of water and I think it helps. I never knew how the slides worked. There is still some sputtering, but maybe not like before. The mouthpiece is Mendini/Cecilio.
Good! Because there's so much more tubing in the horn it collects more condensation than the trumpet, particularly in cold weather. You'll find the tuning slides on the back are the ones you have to empty most often, but also the 3rd valve slides tend to get a lot in because they're towards the bottom. If you blow some air through the horn you can tell if there's water, it'll make a popping sound, and if you then press each valve in turn you can hear if it's in any of the valve slides.
Does your horn have one or two sets of valve slides?