Tag: Bars

…How to control humidity

(Every Percussionist Should Know…)
…How humidity can be controlled.

It is humidity not temperature that has the biggest effect on the tuning of wooden note bars. If you ever read so-called “experts” stating the importance of temperature controlled environments with relation to the tuning of xylophones and marimbas, they are talking rubbish. There is a very simple experiment one can do to test the hypothesis; touch a xylophone bar then a glockenspiel note bar; which one is cold? You probably already know the answer – the glockenspiel bar is cold, but why? Glock notes are metal and metal is a conductor whereas wood is an insulator. This is why radiators are made from metal and window frames are made from wood (or should be).

At the extremes, temperature will have an effect on tuning, but that would be an extremely difficult experiment to isolate temperature from humidity. The main cause of atmospheric tuning related problems is humidity. The big word used is hygroscopic in relation to wood, which means that wood absorbs and releases moisture.

A rule of thumb is that hot things like wood and air, can hold more moisture than cold things. If you are that way inclined (and thankfully some people are) you could create a graph to define the maximum amount of moisture something could hold at any given temperature. The graph would depict 100% moisture content. This state is unlikely to happen to your xylophone or marimba, but they will contain a certain amount of moisture in relation its potential maximum, so this is known as relative humidity.

Finally, because wood is surrounded by air and it is hygroscopic, it will absorb or release moisture until it reaches the same relative humidity as the air. The video I made below explains the ramifications of this and what can be done to control it.


LP Xylophone Notes (Job No: 1242)

Out of the whole family of keyboard percussion instruments, xylophones suffer the most with going out of tune.  There are two reasons, first the note bars seasoning, second from being played.

Due to atmospheric changes wooden note bars absorb and release moisture, as the moisture leaves the wood, it takes a bit of matter with it, so the note will always go out of tune even if the instrument is not played.  However this is more evident in marimba bars which are wider, thinner and more extensively arched, whereas xylophone bars are more chunky and tuned to fifths, or should be, but more of that later.

When xylos are played, hard beaters are used, and these damage the surface of the note bar leaving indentations.  Therefore nothing harder than the note bar should be used to play it, so no hard plastic beaters if the piece has lots of fortississimo.  Furthermore the edges of the bars take a battering, and they become frayed.  When the bars are tuned, I have to remove this loose material, which further affects the tuning.  Eventually I run out of wood to tune the bars, or the internal structure of the wood has been softened or split thus killing the sound, so new bars need to be bought or made.

One last bit to finish off, there is a trend now in new instruments towards thinner bars which have been octave tuned as well as using cheaper woods like padouk.  Wrong, wrong, wrong!  Thinner bars don’t give the stacato sound of a xylophone, octave tuning just sounds wrong – a xylophone has a jarring sound, that is what it is for musically, and padouk is even more prone to damage and splitting.  So not only are they not xylophones, but more like piccolo marimbas, they will not last very long – years instead of decades!  Finally, because the bars are so thin, my job of retuning them is severely limited.

So lets get into the job.  First I get a plank of Honduras Rosewood that will do the job.

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This is then ripped to give me the width.  I got two lengths out of this plank which is enough to do all the notes.

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These batons are then cut down into the lengths required for the note bars, resulting in lots of sticks of wood.   I then plane to faces to get them flat and square.

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I can then thickness them to the correct width and depth.  I now have a pile of equally sized sticks of wood.

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The next job is to drill the holes for the note cord.  It takes ages to set the drill up so the notes are held in the correct place, and flat on the bed of the vice.  Getting the angle right is the easy bit (if you have the right equipment).  However once everything is set it is quick to drill all the sticks.

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I can now put the radius on the edges of the bars.

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Now I finally have note bar blanks which can be varnished and tuned.