[feather_share]Perhaps one of the greatest influences an experienced restorer can bestow on a fine instrument, aside from preserving its value, is setting up of the playing assembly and final voicing. Bearing in mind that the quality of sound is the primary importance for the instrumentalist. It is the restorers aim, through the set up, to achieve an instrument which enables efficient transfer of sound and tone via the interaction of the musician, bow and string. The interaction between instrument and player is both subtle and crucial in tone production and varies from player to player.
For the purposes of this article we can assume that our instrument is otherwise in top condition and that the bass bar is accurately positioned. In addition, we assume the fingerboard has the correct profile. This taken in to consideration, our attention turns to the sound post and its position. Its location is accurately calculated in relation to the treble foot of the bridge. It is common practise to fit the sound post prior to the fitting of the bridge feet, as the sound post solidifies this area of the top promoting a more accurate fitting of the bridge. It is workshop practise to mark the position of the bridge with a white wax marker. Plotting the position of the bridge with the marker gives us a visual reference which assists in placing the post. The marker is inert to the varnish and is removed after the final fitting of the bridge.
As previously stated, the final position of the sound post is behind the treble foot of the bridge and within the outside line. The post, turned from straight grained spruce, is carefully inserted through the treble sound hole with the aid of a curious S shaped tool. The sound post tool allows the restorer easy access to and manipulation of the post through the sound hole. The upper and lower ends of the post are cut to fit exactly the internal contours of the top and the back without any gaps or high spots. A Dentist’s mirror comes in handy for checking the all round fit of the post to the top, maximising contact. We also observe the fit and vertical position of the post through the tapered hole made for the end pin.
Warning. As the post remains in place purely by friction, it is not glued or otherwise fixed into place; the other factor is the tension its position exerts on the back and the top. I cannot stress too much the importance of professional fitting and adjustment of the post. An incorrectly fitted or heavy handed adjustment of the post can cause localised distortion and structural cracks to the top and in extreme cases the back. The presence of which can adversely affect the value of the instrument. So, to summarise, the post must be in a specific place, on the vertical plane, correct tension and the ends must fit the internal contours exactly, oh and the grain is at right angles to the grain of the table and all done through the treble sound hole on the end of an S shaped piece of metal.
Having fitted the sound post we now prepare to fit the bridge feet accurately to the contours of the table. The majority of restorers and makers utilise wedge shaped blanks made by specialist manufacturers, from which we fashion the final product. The aim is to have the whole area of the feet in contact with the table avoiding gaps and high spots. As the bridge is made typically of Bosnian Maple or similar, a timber many times more dense than the spruce of the top, a high spot would compress the soft fibres of the top with the downward force of the strings causing unnecessary localised damage. Many fine old instruments have quite distinct areas of wear and compression in the position of the feet. Again the feet must be fitted perfectly without gaps and high spots even in these worn areas. There are a number of points to consider when fitting the bridge. Namely that the bridge position between the sound holes is correct and that when the feet are fitted the vertical angle is also correct. The vertical angle, when viewed from the side, has the appearance of sloping back towards the tail piece.
Having fitted the feet to the contours of the top, we now set the height of the bridge. The four strings of bowed stringed instruments, tuned a fifth apart descending in pitch from the top string, bear a direct influence on the height required for each string. For example, the highest pitch string has the smallest oscillation when bowed; with the lower three strings having progressively larger oscillations as the pitch descends to the lowest string. This is the reason for the gradual increase in height from the highest pitch string to the lowest. The curve across the top of the bridge is also crucial and bears a direct relation to the curve of the fingerboard, offset slightly to allow a gradual increase in height. The curve allows the musician to play easily on individual strings, with every dynamic, without interference to other strings. We work from a set of accepted measurements for the string height, varying dependent on the type of string preferred by the musician. Pure gut or gut cored strings being set slightly higher than synthetic cored strings.
The next process is the reduction in the thickness of the bridge to the desired measurement. Material is removed from the front surface of the bridge only, with the greatest thickness at the base narrowing to an even thickness at the top curve. In addition, we open out the area around and between the feet. Attention is paid to other areas on the bridge as needed. We further fine finish the bridge with progressively finer abrasive paper and cut a chamfer to the four long vertical edges. The string spacing is set at the point we set the height. The grooves are further worked to accept the individual string gauge. The bridge must not grip the outer winding of the string unduly, as this will reduce the working life of the string. With the exception to a few minor adjustments, the bridge is now complete and ready to be put in to place. The individual strings are put in to position and brought up to pitch while maintaining the bridge in its final position. The set up is now complete.
It is important to remember the individual requirements of each musician. An instrument is set up by us to work as efficiently as possible in a manner each skilled and experienced restorer would accept as standard. Small and subtle adjustments can be made to influence the tone and where needed we work closely with the musician to achieve their ideal sound.