Flat note problems on school marimba - (A Problem from Linda Davis)
-----Original Message----- From: "linda davis" Sent: 30/03/05 7:45:49 PM To: firstname.lastname@example.org Subject: tuning marimbasDear Jim,
I teach music at a beautiful primary school in N.S.W. and have been enjoying Jon Madin's marimba playing books. This inspired me to want to make one for the school. Luckily there was a teacher very keen to to do and he spent the school holidays building a box resonated 3 and a half octave marimba. The problem is the tuning. We have been able to tune the lower bars but once we reached the second octave everything was flat by anywhere between 3 or 4 tones. We chiselled so much off the ends to bring the pitch up that the note sounded totally dead and still not right. The size of the bars have been checked and rechecked so I don't think this is the problem. We would appreciate any advise you can give, I am sure it is something simple we are doing wrong.
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Its very difficult to get a real sense of what's going on with these bars without seeing/hearing them. There are two things that I might guess are contributing to your problem.
Really if a bar is significantly flat you need to make it shorter - I understand that in this case you already have the frame so your options are limited. That is part of the problem. I would usually cut and tune my lowest and highest notes first - find the optimum nodal points THEN build the frame to the dimensions created by those nodal points. If you have a bar that has its nodal point already drilled, and you carve it to significantly alter the pitch - then you will also be altering the natural nodal point in the bar. That means your string (or whatever suspension mechanism) is now preventing proper vibration as it is no longer at a nodal point. This might be part of why these Notes are starting to sound dull.
The two things I suspect off the top of my head would be the thickness of the timber - often not considered when following those directions - and also the type/hardness of the timber. This is where written down directions can go wrong. Timber is a non-standard product unfortunately for instrument builders. Different types or even slightly different bits of the tree or moisture content can make drastic differences in the dimensions required.
I can't really tell you how to proceed without being there, but hopefully this gives you some insight as to where to start, and what you might like to try.
answers by Jim MCCarthy - 30/03/2005
I was reading your very useful site and came across the letter from Linda Davis about very flat bars.
I made Jon Madin's " Minimarimba " (1.5 octave instrument) from his book "Make your own marimbas" and had exactly the same problem of the bars appearing to be very flat in pitch before any carving is done . The problem is actually very simple, Linda (and I) were tuning the bars an octave too high. For example, if I was after a 220Hz A, the bar (before any carving) might be at E (or about 300 Hz) or even higher. What I did, was think that I had to tune to the higher A and so I'd think the bar was actually very flat to start with. . In fact we are meant to tune to the A BELOW the E. I didn't realise at the time that you can flatten a bar's pitch much much more than you can sharpen it (without cutting ends off). So I tuned to the nearest A (440 Hz) rather than the desired A (220 Hz). The tuner I used doesn't give the frequency of the pitch but simply tells you that it is an A and it could be any A and hence the source of my error. Jon suggests to start tuning with a middle bar and play the appropriate note on a piano so you know which way to go but doesn't actually warn that you might tune an octave high if you start the tuning process on the lowest bar (as I did!) with an electronic tuner. Jon happily helped me with solving my problem with a couple of emails.
Jon appears conservative in his bar design and they are meant to be quite heavily carved. I'm amazed how much you can drop the pitch when you carve out the middle!!
I know Linda's email is a bit old, but you may want to pass on this information incase she wants to have another go.
Cheers Richard Evans
follow up from Richard Evans - 6/08/2007
For more help on instrument building you can email Jim.