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On tuning overtones in marimba bars (Discussions with John)

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-----Original Message-----
From: John
Sent: 26 May 2008
To: jim@percussionclinic.com
Subject: Tuning Marimba Harmonics up
Hi Jim! My name is John. I am currently working on a Max Krimmel Fan Bass marimba based instrument out of cherry wood. I've done the rough tuning of all the bars but I've ran into some trouble with the overtones. the problem is that the first overtone is, on almost all of the keys, less than two octaves above the fundamental. Is there a way to tune them up without sharpening the whole bar?

Thanks a bunch,
John


Hi John..
I'm afraid it's not good news from me!
I certainly don't know of any way to raise the pitch of one mode without raising them all - I'm 99% sure there isn't one. CERTAINLY there is no way at all, to raise the pitch of any mode at all, in a SIGNIFICANT way without actually making the bar shorter, which would destroy your nodal positions etc. Once you lower past a semitone or even ˝ a semitone it can be a matter of throw it out and start again. I am surprised you are having this problem with bass bars as usually it is an issue reserved for higher notes. When the starting length of the bar has the overtones already placed too low, it usually means that you need to start with thicker planks which will give a higher pitch overall for a given length.

Something you might like to try is tuning the 1st overtone to ONE octave rather than two. I have never actually done this myself, but there have been may times when I have thought that it might actually be better for a bass instrument. Low notes tend to be slow to pitch - it takes longer for the listener to establish recognition of pitch. A harmonic which is lower but at the same actual note might help in establishing pitch of the bar. Placement at ONE octave should not resonate in the resonator which is as it should be. If you placed the 1st overtone at an octave + fifth then it would and it would sound too reinforced. In some ways this makes the harmonics of the bar closer to those of almost every other instrument - ie a natural harmonic series. The same logic would see the 2nd harmonic work ok at 2 octaves or 2octaves + fifth etc - any even numbered natural harmonic. This helps the ear recognize the fundamental even if the amplitude is not great as the brain recreates it from the harmonics. With normal marimba tuning this does not happen which is one of the reasons it is tough to get a bass marimba loud enough.

Anyway - it is a suggestion… If it is a choice between throwing the bar away and starting again or trying the one octave position I would give it a go and you might save yourself some tears. It might even be better!

Let me know how you go, I would be quite interested.
All the best.
Jim McCarthy


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answers by Jim MCCarthy - 28/02/2008

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