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A R T I C L E S
C E L L O S
C E L L O S
C E L L O S |
Set-up: a four part introduction Part 1 Part 2 Part 3 Part 4: The Bridge, Sound Post and Bass Bar Is your bridge standing up straight? Each time a string is tuned it is stretched or slackened along its length. Whether tuning is achieved using the pegs or adjusters, the string has to move where it meets the bridge. In an ideal world the string grooves in the bridge would be well lubricated, there would be little or no friction and the string would slide cleanly over its groove leaving the bridge standing in equilibrium. In practice there tends to be considerable friction between string and groove, causing the top of the bridge to travel along with the string. How can you tell whether the bridge is straight? Many people look at the bridge from the side to check its position. If you happen to have a great eye and a superb visual memory such checks might enable you to correct small deviations as they arise but I don’t think I would be able to. Another technique of visual inspection is to check for a gap beneath the back or front of the bridge feet. If you spot a gap it is definitely time for corrective action. In fact it was time for action some while ago but it is better late than never. My preferred method for keeping a bridge upright requires some skill on the part of the player and also that the strings slide fairly easily over the bridge. The top of the bridge must be grasped firmly on both sides with thumbs and forefingers as close to the strings as possible and moved forward and backward beneath the tuned strings until the balance of the bridge on its feet can be felt. The bridge should stand neither on its toes nor on its heels but somewhere halfway between. Given practice and familiarity with a particular instrument this process can become quick and painless and should be as integral a part of preparing to play as rosining the bow. Why is it so important to check the bridge? The stance of the bridge really does affect the sound of an instrument. All truly sensitive players I know share my obsession with bridge posture because they can feel and hear the difference when the bridge becomes unbalanced. The moment that the pressure of the treble bridge foot on the front of the instrument becomes uneven, the acoustic relationship between the bridge foot and the sound post (which may be the fruit of painstaking sound adjustments) changes. Also, when a bridge starts to warp and long before it becomes structurally non-viable a lot of energy and power ceases to be transmitted through the bridge. How do you encourage strings to slide easily over the bridge? Straightening bridges was much easier in the days of uncovered gut strings. Metal-wound strings like nothing more than to get a few wood fibres between their windings and then hang on for dear life. The key is lubrication. The string grooves should be regularly and lavishly lubricated with graphite from a soft pencil or, better still, soap from a dried out old bar of standard toilet soap rubbed into the groove. All thin strings ( violin Es, most cello As and Ds) should also have a vellum or parchment stuck to the bridge beneath them to stop the string cutting down into the wood (those plastic sleeves are not really a substitute - they generally don’t sound good and don’t stop the string from cutting for very long). Is there anything else to watch out for? The position of the bridge feet is terribly important. When an instrument is set up by a luthier the relative position of the bridge feet to the sound post and the bass bar is of fundamental importance; if the bridge feet are subsequently moved the integrity of the set-up can be undermined. Cellists often come to me because their instruments have had a knock and, although they are undamaged, the tone has changed because the bridge has moved across the instrument. String clearances on the fingerboard can also be affected by a change in bridge position, making the A string uncomfortably high and causing the C string to clatter on the fingerboard or visa versa. The bridges on student instruments often end up moving a great distance, sometimes because the bridge has fallen down completely and has been set up again in the wrong position. Sometimes string heights are too low and the bridge position is changed to make the instrument playable without recourse to a luthier. There is nothing inherently wrong with moving the bridge, but if the instrument is to speak at all well the sound post must be moved to a new position in order to maintain the relationship between bridge and sound post. Is that all there is to bridges - position and straightness? Not quite! The quality of wood and the design of the bridge can make a huge difference to the tone and responsiveness of an instrument (too huge a subject to cover here). What about the sound post? The word ‘sound post’ doesn’t really do justice to its crucial function. The Italian name for sound post is ‘anima’ which translates as ‘the soul’, and indeed an instrument cannot come to life until the sound post is fitted and working properly. My most profound experience of this phenomenon was with the first cello I ever made. While I was still at violin making school I fell in love with a great Italian cello being played at a quartet concert. I met the player, a distinguished musician who had the instrument on loan, got permission to copy the instrument and some months later travelled to London full of excitement and apprehension to know what my friend would think of my cello. Well, he admired, he played and he prevaricated, we admired the original, made coffee and in due course it was time to go home. He kindly gave me and the cello a lift back to the tube station. In the end I could bear it no longer and asked him directly what he thought of the cello. His response “Well, Robin, this is your first baby.’ Some weeks later, at the Manchester Cello Festival, I took my cello up onto the concert platform for a sound adjustment demonstration by the renowned New York luthier René Morel, assisted by a famous cellist. As it happens, his adjustment of my cello was a great success. I can still see the look of amazement and interest my cello received from the maestro after the adjustment, and, on a plate, I was handed the most important lesson of sound adjustment. Morel had moved the top and bottom of my post outward some considerable distance thus forcing the front and back plates of the instrument apart and completely changing the response of the cello. Where previously the cello had a wonderful gravelly C string but had diminished in power from there upwards, now the A string was focussed and powerful and could support the strongest player. Shortly after the awakening of my cello, my friend had a temporary disagreement with the owner of his borrowed cello and was happy to play my ‘first baby’ in all his concerts for a period of several months…. And the bass bar? When people think about set-up and sound adjustment they very often think only of the bridge and sound post. The strength, position and character of the bass bar is also an important part of the equation. But there is an obvious reason why the bass bar is often taken as something to be worked around: changing the bass bar entails removing the front of the instrument and it is expensive. Bass bars are usually changed on valuable instruments with tonal problems, when an instrument is open for another reason or when the existing bass bar has proved to be insufficiently strong causing the front arching to become distorted. © Robin Aitchison 2001. Published in ESTA News & Views Autumn 2001 All rights reserved. No part of this publication may be reproduced, stored in or introduced into any form of retrieval system, or transmitted in any form or by any electronic, mechanical or other means, including photocopying and recording now known or devised hereafter, without the prior permission of Robin Aitchison RETURN TO TOP GO TO ARTICLES HOME PAGE
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