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[RGF]

Hi, all.

I've been doing a bit of refurbishing on an old red Hohner G/C Erica, including a complete retuning to a somewhat drier sound. I'm a relative beginner at tuning, but I've done maybe a dozen or so, mostly piano accordions up until now, and I'm confident enough to at least work on my own instruments. But this is the first such puzzle I've encountered, and it took me a looonng time to stumble on the answer.

The problem was primarily with the D4 reeds. I'd tuned them to their proper relative pitches, and the beating rate was right in line with their neighbors. But there was a strange "wah-wah" kind of sound that I can only describe as a fluctuation in volume, as if the frequency of the beat was correct, but the amplitude was too great. I replaced the valves and rewaxed the reeds and checked the tuning again, but the problem was still there.

In desperation, I substituted new reeds, and tuned once again. I'm using Dirk's tuner, which enables you to sound both reeds simultaneously in the accordion - Neither reed was off by more than a few of tenths of a cent, and the deviation from the target beat rate was less than .1 herz. But still that thrumming kind of volume thing going on. So at this point I'm left concluding that there's perhaps some strange resonance going on with the instrument itself, but what?

Got to thinking about resonance, and recalled reading someplace about the purpose of those little braces that span between the tops of the reed blocks, connecting them to one another. So just on a chance, I screwed a little spanner between the two blocks, just at the location of that reed, and BINGO! A scrap of stiff plastic and two small screws and five minutes work, and the problem disappeared.

Anybody else ever experienced anything like this? Can anyone shed some light on exactly what was going on here?

What a relief to finally have this one behind me. Would have been nice if it hadn't taken so long, though!

Bob

[Stiamh]

Hi Bob

I have never attempted to tune a box, but Richard Morse (of the Button Box) describes exactly what you are talking about on this page: http://www.accordionpage.com/wetdry.html

Reeds which are mounted closer together or more loosely secured (heavy wax, softwood banks, thick felt bank gaskets) will tend to make an adjacent reed of similar pitch beat in unison, sometimes pulling together reeds 10 cents apart to the same pitch resulting in a "waaaaahhh, waaaaaahhh" sound as they come together and break away.

Steve

[RGF]

Steve,

I seem to recall having read that bit some time ago, but had forgotten it completely. Thanks for redirecting me. The phenomenon that he describes is exactly what I was experiencing here. The two reeds, although tuned about 15 cents apart, did on occasion pull together until the tremolo all but disappeared. The rest of the time it just wah-wha'd at me!

Since the reed pair is in back-to-back chambers, and since one of the screws for my brace kind of goes right down into the center wall that seperates the reeds, I'm curious now if the actual connection the adjacent reed block is what did the trick, or if just stiffening that surface in some other way might have done the same trick. i.e. just a long thin screw down into the center wall, or laminating that bit with a small bit of thin ply or some such.

But I've spent so much time on this, that my curiosity is going to remain just that. As long as the problem is solved, I've no real interest at this point in further tinkering to determine just what part of the patch actually provided the cure. Maybe next time!

Bob