Chu Alto Intonation Quirk: Diagnosis?

[Hornlip]

Let's say I've got a '29 Chu alto with a modern Meyer 5M/M mouthpiece. I'm playing middle G and the intonation is perfect. I go down a half-step & play standard F# with my right middle finger: perfect intonation. I go down another half to F: 2 cents sharp. Down another half to E: Waaaaaay sharp!! Down half to E-flat: Way sharp. And then, D: Perfect.

:(

Intonation is otherwise solid on this horn, and respectable up in the palm keys. The D, E & F keys do look like they're adjusted too high -- they feel it, too. I suppose that could be it. Otherwise, what gives? Any notions?

[Lomar Manx]

put a tuning crescent in the top 1/4 of the E and D tone holes. You will have to trial and error to determine the right size. Key height has next to nothing to do with intonation once the keys are open more that 1/3 the diameter of the tone hole. The palm key problem can be helped by installing tuning crescents there, or by building a mechanism that looks like this

http://www.saxgourmet.com/images/Cmechanism.jpg

that partially closes the c pad when you press the octave key, thus flattening the palm key tones.

[Hornlip]

"Tuning Crescent"? :shock:

Hmm. I know a little, but not enough, to know what a tuning crescent is or where I can get one!! Much less install that bar -- I'm no tech!!

Are the tuning crescents something an amateur could futz with, if he could find one?

[shmuelyosef]

You can just go to a hardware store and buy some sheet brass (maybe .015") and cut a crescent sized slice with an outer diameter the size of the hole. You can experiment on the size/width using putty, chewing gum etc (tiniest amount) until the horn is perfect, then just 'tack solder' them in place. I just solder three places (middle and two corners). I do this with old Kings, too, which always have really weird intonation problems.

[MusicMedic]

I use the Tuning crescents on instruments a good bit. They work just great.

The basic idea is that crescent moves the top of the tone-hole further from the mouthpiece. I use a piece of 1/16 cork. Press it on the tone-hole for an impression then cut out the cork crescent.
Contact cement the crescent into the tone-hole and the pitch will become lower. It's about that simple. Lowering key heights will have an effect but at some point (which is easy to figure) the tone will get stuffy and loose it's brilliance. At that point, if the tone is still sharp, you can add a crescent.

Here is the danger:
If your horn is not set up well, you will be adding crescents all over the place. THe key heights need to be right before you begin this work otherwise you're in for a long road. Note that the intonation of any note is relative to the set pitch of the tuning note. So, by changing the tuning note, you can change the intonation of the whole horn drastically. I have come across instruments where it would appear that several notes were very far out of tune. Then, by changing the Tuning notes' intonation, the instrument played more uniformly.

There is a shotty scetch of a tuning crescent on this page:
http://www.musicmedic.com/mm/tuningkit.php

I hope that helps!

[Hornlip]

The basic idea is that crescent moves the top of the tone-hole further from the mouthpiece. . . .

Ahh--now I get it.


Here is the danger:
If your horn is not set up well, you will be adding crescents all over the place. THe key heights need to be right before you begin this work otherwise you're in for a long road.

I'll give it a try, but I think the keys on the lower notes are definately adjusted a bit too high. When playing an E you can depress the D quite a ways before the tone/tuning is affected at all. However, I'll leave that kind of work to a pro.

Thanks for the input, all!!

[MusicMedic]

I'll give it a try, but I think the keys on the lower notes are definitely adjusted a bit too high. When playing an E you can depress the D quite a ways before the tone/tuning is affected at all. However, I'll leave that kind of work to a pro.

Not a bad idea to leave it to a pro. But, you might want to have the key heights at a good place. Then get used to the intonation. Only then would adding a crescent be a really sound idea. If you start changing the location of tone holes with the rest of the horn in poor adjustment, you might end up doing somewhat of a run around.

It's best to get the horn working it's best THEN try and improve it.

FYI, the key heights on the bottom hand can be lowered simply by adding something between the key feet (3 total) and body. Maybe a little clear tape will get you started. You could get the heights where you think they are best, then take it to a tech to make your heights "permanent" (impossible to do with cork). Then, add the crescents.


Good Luck.

[Hornlip]

It's best to get the horn working it's best THEN try and improve it.

What, and deprive myself of balling the whole deal up while tinkering with my horn until I'm so frustrated I throw it in the case, forget about it for six months, then ship it off to a real horn tech? Killjoy. 8)

[les]

It might also be the case that the low notes are not necessarily sharp. It could be that the notes above the ones in question are FLAT. If these notes were brought in tune with the lower notes, then a mouthpiece adjustment might be all that is needed (pulling out). Like the man says, get the horn (key heights) adjusted before installing any crescents. could save a lot of trouble.

[werkinsnake]

While we are on the topic of early CONN repairs, I have a 1923 NEW WONDER alto in Nickle plate. I use a new Otto Link 6* mouthpiece, Rico Royal size 3 reeds, and Rovner Lig. My problem is with the low Bb and B. They both gurgle, particularly the B. I thought that it may be an unseated pad, but they all look fine. I've checked with a leak light on anything that would possibly effect the two notes. Could it be a bell misalignment? Bad mouthpiece to old horn combo? Defect in the split bell key design? If anyone has any ideas please let me know. Thanks.