Ask Dave: What Can I Do About a Horn that Plays Flat?

Eric J asks:

I recently bought a new horn about two months ago. Everything is in working order, great sound, projection, ergonomic, light, just a great instrument overall. There is only one problem: The Bb side of the horn is consistently about 15 cents flat.

All the slides are pushed in, the F is still a bit flat but not near as severe Bb. It’s an annoyingly apparent problem, with the rest of the section being sharp almost all the time. It’s just a struggle. Is there a way to shorten the tubing or what can I do?

Dave replies:

A brass instrument that plays flat is almost useless unless it can be sharpened and made to play in tune with your ensemble.

First, let’s ask the “is it plugged in?” type of questions. Can you play in tune on other horns? If so, then the problem lies in this horn. Does this horn play out of tune with other mouthpieces? If so, do other players play flat on this horn? Does the horn play flat with your hand out of the bell? If all the answers are “yes”, then the problem is likely with this instrument. If not, consider a mouthpiece change, a hand position change, or a change of instrument.

Now, let’s assume you’ve ruled out all the other factors that might make the horn play flat, and you still believe it’s the instrument. Before we cut tubing to make it play sharp, let’s consider other things that might make it play flat, the most likely one of which is leaking. Either you or your technician should check for leaking slides, solder joints, or rotors. If the horn is tight and because it’s new it doesn’t have any damage, then we end up with the last consideration: cutting tubing.

Which tubing to cut is the main question? Any tubing cut must be to the cylindrical tubing. That starts at the main tuning slide just past the mouthpipe and ends just before the first branch after the valve section. Because both sides play flat, a cut to the main tuning slide legs and slide stockings should be considered.

Since the Bb side plays much flatter than the F side, it should be evaluated as to whether a cut to the Bb connecting tubes can be made, as well. Determining the length and positions of the cuts is technical, so I won’t discuss it here.

But do note one important point: if you cut the tubing to make the overall horn sharper you might move the nodal points in some harmonic series and, as a result, make some notes play out of tune. This is a slight, but real risk. Cutting the horn should only be done after all the other options have been exhausted.

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