Tuning technique of the marimba

[FanYang]

Hi there,

I've seen a few tuning technique of the Adams and marimba one.
1. Cut the X gap on the underneath of the bar(use the table saw).
2. Cut a small gap on the underneath which between the node point and end( specially in the first octave of the bars).
3. Some one says they tuning the second overtone that ten cents lower.

Does anyone can answer me why they does that?

Thanks 

[Jim McCarthy]

HI there FanYang - good to have you here!
I'm not quite sure what you are referring to when you say "X" gap - can you possibly explain that a little more?
You also say that there is some material removed from under the bar but at the END of the bar - you mean on the outer side of the string hole? If so that would have the effect of RAISING the bar's pitch - not lowering it. Generally speaking when raising the pitch of a bar it is almost impossible to control which modes get raised by how much - they all get raised together. One raises them all then brings them down selectively by removing material at the various select points BETWEEN the nodes. Even so - raising should not really have to be done at all - generally if this is done, it means there was an error in the initial tuning stages.
Jim

[FanYang]

Thanks Jim, i don't think that Adams cut the single gap or small groove to raise the pitch, because the BERGERAULT does something too, but the BERGERAULT has cut two small groove before the node point ( specially on the lower notes).   About the X groove or X gap that ill find the picture to you.

[FanYang]

Hi Jim, is something like this.

[Jim McCarthy]

Oh - right - yes I have seen  this many times. Usually though historically it tends to be on cheaper Orff instruments where the bar dimensions are less than ideal for the fundamental bar pitch. I am surprised to see it here. As far as I am aware this is a method used to control a completely different type of overtone - a TORSIONAL mode.  have personally never had an issue with a marimba bar made to pro standards that required this technique - though from time to time with diatoninc school instruments.

[FanYang]

Hey Jim,

Could you please tell me why they are use this kind of overtone technique? Whats the different there ?

Thank you