All violins, even the finest – old or new – periodically need to be checked for their tonal health.
Instruments are exposed to the hot or cold, dry or humid air, to the warmth of the player’s body, to the constant vibration, to the changes in seasons accompanied by variations in ambient temperature and humidity. As the ambient humidity changes, the instrument may swell or contract, the soundpost once in its perfect place may gradually slip out of its place and even if it is only a fraction of a millimeter it will certainly affect the quality of sound. The fingerboard may go up or down or develop groves which affect the ease of playing. Most of these problems accumulate gradually and the player is frequently aware until it becomes difficult to get the sound out of the instrument. Still more frequently: the player, specially a fine player, becomes aware there was a problem only after it is removed.
Tonal adjustment consist of non-invasive, tiny modifications to the position of the sound-post and the bridge.
Rarely it may involve making a new bridge or a new soundpost, or re-surfacing the fingerboard, adjusting the length of the tailgut and such. If you feel that your instrument is out of balance, if certain strings or only certain notes sound duller than the rest, if you feel the sound has become too dry, to loud, too sharp or acquired whatever other undesirable quality – for your way of playing – it may well be a good time for a tonal adjustment.
Periodically bringing your instrument for a tonal adjustment may also help to spot more serious problems on their early stages of development.
I work on tonal adjustments with care verifying each step with the musician, asking him or her to play the instrument after each modification.
Being a confident player I also let the musician hear the instrument from distance by playing it myself. I take the quality of sound as seriously and as sensitively as any musician does, consequently I spend as much time as necessary for getting the best possible result, as close as possible to the musician preference.
However, a typical session of tonal adjustment does not take longer than an hour, when it is limited to the overall check and adjustments to the position of the existing bridge and the sound-post.
Unless completely justifiable and inevitable, I do not recommend interfering with or carrying out modifications on any original parts of the instrument. I recommend checking your instrument at least twice a year, once the seasons completely settle or after an extensive traveling.