Intonation

When you have the chance to play old instruments and notice the idiosyncrasies they demonstrate, I at least begin to wonder whether they always played that way or whether over the course of time, they have been affected by the passage of time. And it is interesting that different horns demonstrate different intonation issues. Euphonium examples:



1894 Distin - Flat on middle C and sharp on high F



Olds Studio - very flat on tuning note Bb harmonic.



Woodwind&Brasswind - plays reasonably well in tune until you get to the low Bb (not pedal) and below which go very sharp.



I assume that the W&B was always the way it is.



But I was very surprised at the Olds, as I'm sure that most Studios would be very well in tune. And I don't know what might be wrong to cause it to do that.



On the Distin, when I first played it, I thought it had reasonably good intonation but recently when I tried, I found the intonation issues. I can't think of anything that would cause it to go out, so I must assume that I just didn't pay close enough attention first time around.



So, what might affect intonation? I assume that leaky valves would make pitch a bit "soft" and tone airy, but not pull certain notes out of tune. Similarly, dents and build up inside the tubing would make the horn just make the horn less responsive. And valves out of adjustment would just make notes more difficult to sound.



Any ideas of things that might make the intonation of an instrument "slip"?



Reply #1 - Jun 23rd, 2007,

Worn valves can. if the leak causes the loop to be in function, when it is not supposed to. An internal leak. With rotary valves, the loop can partly come to function even if the valve is released. That is the main problem when rotary valves get untight, leaks to free air are not so common in these valves. In piston type valves the loop is more likely to act as a dead end-branch off if untight.



It is possible to get a hint on such a problem.



First remove all valve slides and exercise the instrument through the natural "no valve pressed" scale. It should act the same, both with and without valve loops, if not, there is an internal leak i the valve.



More tricky intonation-offs are only present in some cases, perhaps just one single tone. Try to remove valve slides on valves not actively involved in that tone. Any change in performance indicates an internal leak.



No brand can free themselves from natural laws. Or they would have made the perfect horn already a long time ago. Horn making is making compromises, and weigh evils against each other. Some intonation faults are likely to have always been there.



Forgot to mention that internal leaks can occur in both piston and rotary types of valves when the valve is pressed. Then the mainstream takes the loop, while something takes the shortcut. There is no easy way to diagnose that, except for a careful valve inspection.



Put a very thin layer of marking blue on the inside of the valve housing, and then in goes the valve, pressed fully down, and out it goes again. The blue should now be visible all over the surface of the valve stem, also between the air holes. Unmarked surfaces are an indicator of a possible internal leak.



Blue marker is (any) artist color in powder form, solvable in oil or turpentine. Water solvable colors won’t work on valves, they are too thick, and will not hang on to the metal, least of all if the metal ever was in contact with a lubricant.



Blue is commonly used, as it contrasts well with both brass colored as well as silver-colored surfaces.