Tag: Tuning

Xylophone Tuning (Job No: 1294)

On the surface, many aspects of my job seem to be structural or mechanical, which they are, but the solutions are always to improve the musical aspect of the instrument.  Aside from increasing its lifespan, which is almost a byproduct, the main aim is to improve playability, projection, tonality, etc.  Right at the very heart of this is the tuning.  I have been working on and off on a series of articles to explain the various aspects of temprements and tunings, and they will eventually be completed, but what I realised was that I very rarely write blog posts about this aspect of what I do.

Sometimes my self protectionism manifests itself inadvertantly with a reluctance or resistance to publicise what I am doing and how I go about jobs.  This is irrational, because the reality is that even if I were to tell someone exactly how to do something, they can’t necessarily do it.  I have experienced this many times when I am on the phone to a customer talking them through a job, or even face to face teaching my past assistants – there is an empirical feel that simply cannot be taught it has to be learned through experience.  Tuning is the same, in that there is an empirical understanding of what to do.  There are plenty of misleading internet guides on how to make your own marimba or xylophone, and if you have the time, energy and don’t mind making something shit, then they are great.  However to expect an app on a mobile phone to be capable of tuning percussion instruments accurately would be naive.

So anyway, all the notes are unstrung and arranged chromatically.  I have a bench that houses trays which contain a complete instruments note bars which can be slid out to be worked on, or be put away until the following day.  It keeps everything together so that I don’t mix up the instruments.  The work bench has a top and two shelves so that when I work on a set of notes the octaves can be separated vertically up the bench.  This means that I can tune any of the octaves chromatically, or do all the Cs, all the Ds, etc in a compact space, because I do jump around selecting various notes to do side by side comparisons.

When I start tuning a set of notes I am listening to the notes with my ears as well using electronic tuners. The tuners enable me to tune the bar to exactly the pitch I want. Qualifying what I mean by exact, the tuners I use are accurate to 10th of a cent, and a cent is a 100th of a semitone, so in other words ridiculously accurate. In practice, for wooden note bars, the tuning tolerance can be greater, so I tune to within a cent of the pitch I want.

On the first day I am listening with my ears more in order to identify any issues and inconsistencies. Sometimes there is a suppressed feel to the way an individual bar sounds, and often there are slightly discordant harmonics. Additionally xylophones in particular are prone to edge damage, so all of these factors help determine how I go about removing material from the bar. Since removing material is the only way I have of manipulating the tuning, this first day takes the longest because if I get it wrong, I can’t put the material back onto the bar.


Over the following week I return to the notes each day, making smaller and smaller adjustments until they have stabilised, at which point I seal the underside of the notes with lacquer, restring them and return them to the instrument frame or the customer.

…How your timpani has gone from sounding good to bad.

(Every Percussionist Should Know…)
…How your timpani has gone from sounding good to bad.

My intention with this article is to explain how your kettle drum works acoustically to create a harmonic pitch.  I have simplified everything considerably for clarity and brevity.  Once the fundamentals are understood you will then be able to find out what has happened to your drum, and come to the realisation that you really do need expert help!

Right at the very beginning, Preschool Paul, whilst out walking with his parents threw a stone into a pond and watched the ripples.



Because this pond just happens to be perfectly round, the ripples bounce back off the banks uniformly.  It creates a nice symmetrical pattern.  When applied to your kettle drum, this would represent the perfectly pure note.  The stone represents the timpani stick and I know a timpani is played at the edge, but that is because of more advanced acoustical reasons which do not contradict this acoustic model.  The ripples are sound waves.

However, if the pond was elliptical then some sections of the circular sound wave would be reflected off the bank before other sections.  Your drum now sounds awful because the interaction between the original and reflected sound waves are inharmonic. (This will be explained in another article if I ever finish it!)  The same thing would happen if your timpani bowl has been squashed and you have a flat spot.

wpid-wp-1435049671973.jpg

However it gets more complicated, because we live in a three dimensional world.  In the diagram below, the drum looks circular when viewed from directly above, but as the image rotates around the centre line as if to view the bowl from the side, it can be seen that the top half creates the expected ellipse, whereas the bottom half undulates up and down.  This could be because something has dropped onto the drum from above.  At the bottom left you can see the “acoustic” shape that this bowl would create.

wpid-wp-1435050147365.jpg

Because the bowl shape doesn’t vary when timpani are played, then any defect in the roundness of the bowl will affect the entire playing range.  It is relatively easy to return an elliptical bowl back to round – I do it every time I change a head, however if the bowl is egg shaped things suddenly get harder, and if it’s not flat they become harder still.

Timpani don’t just play one pitch, they have pedal mechanisms that adjust the tension of the head.  Now we know how to get a good note, it is easy to understand that if the tuning linkages are pulling one part of the head harder than another, then acoustically, this is like changing the shape of the bowl away from circular and harmonic.  This manifests itself when the kettle drum sounds good at one pitch, but gets worse as you move away from that pitch.

However, timpani always sound better at lower pitches, so a 26″ will always start to sound a bit iffy at higher pitches because they are no longer capable of working properly from an acoustical stand point, and anything smaller just doesn’t work.  As players, you will probably agree with me in wishing that composers would stop trying to get timpani to play top A’s and above – they would be better using a roto-tom!

Adams Universal Timp Problem (part 2) (Job No: 1243)

This post follows on from Adam’s problems (pt 1).

So day one was mainly spent setting up the drums, and making the bottom blocks.  Today starts with finishing the installation of the other two blocks, before making more components.

The original central tuning rod has been removed from the pedal, and is now actually central held by a guide block.  So now I need make a secondary linkage to join that rod to the pedal.  I still have an attachment on the pedal, but nothing on the central rod, so this is where I start.

wpid-photogrid_1423126221807.jpg

Going through the photos, I take a length of brass stock and the rod end which will go on the end of the linkage rod from the pedal mark everything up and drill lots of holes in it.  (There are an awful lot of Rod’s around!)  After the smaller perpendicular holes are drilled, the pieces go in the lathe to have the longitudinal hole drilled.  The fixings holes are tapped, then the longitudinal hole is reamed to make sure it is round and will fit nicely on the central pull rod (There is only a 0.02mm gap all around so it will be tight).  Lastly the components are preassembled.

Next I make the linkage rod which is simple, I just have to run a thread on the end.

wpid-wp-1423127586300.jpeg

Finally I can assemble the parts on the first drum and check that I have all the clearances, which I didn’t.

The problem is that manufacturers make product and forget that they are making musical instruments.  A lot of effort is put into making new ranges of more, essentially shit instruments, in an attempt to generate the desire to buy in a limited number of consumers.  Very little effort and value is put on the making and assembly of those instruments.  Cheap materials are used wherever possible, and because people are expensive, the cheapest possible labour is used.  So your pride and joy was probably assembled by monkeys, the dregs of society who get pissed at lunchtime and are still high the morning after.  They work for a wage packet, they don’t give a toss about whether the holes are right, it’s the near enough attitude, and near enough is not good enough to make something that makes musical noises.

So when the bowls are put on the cradles, they can be out of alignment by over an inch.  I can compensate, or remount the bowls with new holes.  I choose to compensate.  So in this instance I had remount the connection on the pedal, then make another rod, then further modify the pedal, then reassemble to check, disassemble, modify the pedal………………………..

The final part of this job is Adam’s Problems (pt 3)

Premier Xylophone (Job No: 1079)

An old Premier xylophone in for tuning and repair.
20121031-104534-AM.jpg
There are two main design issues with this instrument, and a further complication:
The note rails sag in the centre mainly because of the joint, but fundamentally because thin wall tube isn’t strong enough. The simple solution is to weld the joints in place to create a fixed rail.
The second design problem is that the resonators act as a structural component of the frame; this is just silly, doesn’t provide strength and is an example of how instrument manufacturers fail to understand the rigours of life as a xylophone and how they are used.
The complication is the round tube on the lower transoms which hold the castors; again this is just a silly idea which makes caster renewal needlessly difficult.

So this frame wobbles all over the place, and investigations show that whoever repaired it in the past didn’t understand the forces in play.

Newtons Mechanics: p=mv

p is the momentum or force, m is mass, v is velocity. Ignoring units of measurement a 60kg xylophone being wheeled along a corridor at 3mph (slow walking pace) will triple the mass to 180kg.

Put the castor at the bottom of long lever (frame leg), and that 180kg is multiplied again.

Understanding these principles explains why bolts shear, frames break, castors fall apart on commercially produced instruments.

However, understanding the principles also gives the solution for me to make the repairs that will last. I am happy to sacrifice the lifespan of a caster to save a xylophone, that is easy to repair, use stronger casters.

Back to the xylo.
First job is to make new lower transoms that are fit for purpose, and will make the rest of the frame easier to strengthen; solution = square tube

20121031-112443-AM.jpg

B&H vibe tuning (Job No: 1070)

A set of vibe notes in for tuning.

On the graph, the X axis are the notes – this vibe goes from C to F.  The Y axis are the cents above and below the zero line which is at A=440 Hertz.  The fundamental pitch is the blue line which is generally flat (to be expected as the instrument is marked A=439Hz).  However the red line is the 2nd Harmonic, and as can be seen it goes from massively sharp in the lower octaves of the instrument, to massively flat in the higher notes.

To bring the notes into tune both of these lines should read zero.

 

Adams Xylo Tuning (Job No: 1071)

Another xylo in for tuning.
20120913-080443-PM.jpg

There is some edge damage on the accidentals in the middle of the instrument. Close up below:
20120913-080623-PM.jpg

The white residue is superglue – precisely the wrong thing to use. Although it is available in different viscosities, the most readily available brand is way too thin, and penetrates too readily then dries and crumbles internally. Furthermore, nothing else sticks to it including finishes.

As each note arrives at its first tune, it is inspected for damage.

20120913-095545-PM.jpg

Difficult to see, but at the right of the arch, the edge is splitting. This needs to be broken out – glueing is just not going to fix the problem, the crack could be deeper than can be seen from the surface.
20120913-100629-PM.jpg

As soon as the investigation starts, it can be seen that the splits are deep.

http://www.youtube.com/watch?v=W5WGjVi5cwY&feature=youtube_gdata_player

First I break out fibres with a knife, then I often cut them away on the sander. Next I rasp the surface using a random cut rasp; this picks up any residual loose fibres. Then file and sand it smooth ready to be tuned and finished.

However, this note was still dead, a sure sign that there is a crack. A face crack was found:
20120913-101554-PM.jpg

Again, this has to be picked out to see how deep the crack is:

20120913-101743-PM.jpg

Looks drastic, but the note is dead, so there is nothing to lose. This just lifted out, but all around the wood is just falling apart. In for a penny, in for a pound…

20120913-102010-PM.jpg

This demonstrates exactly what I mean about internal damage. This is a very badly damaged note – I suspect that it could have been caused by bad seasoning of the wood.

20120913-102416-PM.jpg
It is clearly deep, but the note is now resonant, and therefore can be tuned and played until a replacement is obtained. Also observe the direction of the grain on the end of the bar, not ideal especially on xylophones.

Bergerault Xylophone Tuning (Job No: 1059)

Due to the use of hard beaters, xylophones are prone to face and edge damage.
Whilst it is easy to see the wood splintering at the edges, damage to the face is harder to see, but both will reduce resonance, and of course affect the tuning.
Vibrations don’t only travel along the length of a note bar, but also across the width and through the depth. The grain of the wood runs up the length of the bar. Below is an example of the cellular structure of hardwood:
20120907-115219-AM.jpg

In general the cells are lying like long strings of sausages alongside each other, stuck together with cellulite. Vibrations go along the length very easily, but meet more resistance going across the strings of cells. A crack creates a void that the vibrations cannot cross. So depending on where the crack is will determine whether anything can be done.
Glueing the pieces back together is not practical, but also will not solve the problem. A crack through the entire depth of the note means a new note, any repair will be temporary – the wood will always be trying to get to a relaxed state, glueing and clamping is stressing it.

20120907-120359-PM.jpg

So the only option is to remove any loose wood that is dampening the sound. As it is removed, the improvement in resonance can be clearly heard. It looks drastic, but the note is useless as it was, and repair is cheaper than making a new note.
The photo shows that the left hand edge has been cleaned up, but the note still didn’t sound, so the face was examined, and a crack discovered. That groove in the face is about 3mm deep.

Adams Marimba Tuning (Job No: 1069)

A west end show is going on tour and they have a marimba tuning problem; the marimba is tuned to A440Hz, but the musical samples are recorded at A442Hz. So the notes have come to me for re-tuning.
During the first cycle of tuning, I make a record of where the notes are presently, the results are below.

20120902-012325-PM.jpg

In the graph, the two smooth lines represent what the tuning should be, and where I need to raise the pitch to. The wiggly lines show that the tuning of the notes is actually all over the place.
The biggest problem area is the third partial which is consistently flat.

In simple terms, to raise the pitch, the note needs to be shortened in length, removing material in the centre of the note increases the flexibility of the bar, which lowers the pitch. It is harder to raise the pitch than to lower it, furthermore, shortening the length affects all the longitudinal harmonics, whereas harmonics can be somewhat targeted when tuning down.

Therefore, I raised the pitch of these notes so that all the harmonics were at, or above the target pitch, then the harmonics that were sharp were brought down into tune.