The bridge on orchestral string instruments is where the strings rest between the nut and the tailpiece. There are many aspects of the bridge that need to be considered when cutting and fitting one onto an instrument. If any of the aspects is either overlooked, left out or done incorrectly then you will likely experience one or more of many possible problems.
Depending on who and where it is cut and where they take their influence from, there are many ‘styles’ that may be observed. Apart from ‘stylistic’ influence, the instrument itself largely dictates how the bridge should be cut according to its own properties and measurements.
For example, as a general rule, French cut bridges will be perpendicular to the top of the instrument at the back (facing the tail piece) and English cut is in the front of the bridge (facing the fingerboard). In some cases, which seems more logical, is to cut it equiangular on both sides so that adjusting the bridge becomes easier to see, set and maintain on the instrument.
The above examples then need to be cut to work with the instrument’s direct influences on how the bridge needs to fit. There are a few things to take into account here:
- Projected height of the fingerboard determines the relative string height.
- If the fingerboard has an incorrect bias to either the left or right then the strings need to be positioned to centre them as far a possible. This will mean that the strings will be placed, evenly spaced between one another, but offset to either the left or the right of the bridge edges.
- If the feet of the bridge are not cut flush to the table (top) of the instrument then there will be a loss of frequency transfer which may dull either or both sound and responsiveness.
- If the top of the instrument has wear ‘holes/ dips’ where the bridge stands, then the feet will need to be cut with a protrusion for a flush fit. This is one of the hardest adjustment cuts when fitting a bridge because it comes with its own set of variables that influence how the bridge will naturally stand – there can be no bias to either a front or backward leaning.
- If the bridge feet are cut with opposing angles then the bridge will warp over time and the contact areas will be forced to press down unevenly which will also influence the sound.
- When the front and back, left and right side relationships are cut unevenly then warping will occur on the vertical surfaces which causes the bridge to lean forward on one side and backward on the other. This will have a subtle influence on intonation and a direct influence on how string pressure is exerted on the top that influences sound.
- When the feet are cut with an angle that is bias to either the front or backward leaning directions this will force the bridge to either bow forward, with eventual potential breaking, or lean past 90 degrees backward which will end with the bridge resembling a wind sail on a boat.
- Thicknessing of the bridge has a direct influence on the response and sound of the instrument. Too thick will have it slow and muffled and too thin will have it weak and potentially shrill. Too thin can be regulated with the sound post and string choice but is not ideal.
- In some cases when the wood is soft and/or of poor quality the strings cut into the bridge over time and cause the strings to become to close to the finger board. This may happen with a good bridge as well, although, mostly under the E string if there is no protective lapping or a piece of tubing on the E string to stop it from direct contact with the wood.
- If the bridge is cut too high in relation to the fingerboard it will be uncomfortable to play the instrument with the strings high above the surface … you will then need to press down harder for each note making fast or easy playing near impossible. Of course, too low will be super comfortable but will more than likely buzz when playing forte
The wood quality for bridges is also import and has a noticeable influence on the durability, sound and responsiveness when playing. However, in the case of badly made instruments with thick polyurethane varnish that sound shrill, a soft ‘tomato box’ bridge can help with dampening the sound.
Below there are a few examples of how to detect if the cut of your bridge has problems that influence the durability, playability or sound of your instrument: