Wolf Tone

A particular type of resonance often associated with stringed instruments, especially the cello, violin and viola. Wolf tones occur when the resonant frequency of a vibrating string and the resonant frequency of the vibrating body of the instrument interact with one another in such a way as to produce a new, unwanted beating tone that occurs simultaneously with a note being played. This beating isn’t really a new note being introduced, it is just the sound of beating that occurs when two notes of nearly (but not the same) pitch are played together. For example, a note played on an instrument may modulate its volume excessively – this is often the result of a wolf tone. It is often a distracting and thus unwanted phenomenon; one that string players have been plagued with for centuries. One attribute of “better” instruments is that the wolf tone lies between two semitones and thus rarely becomes much of a problem so long as the instrument is tuned to proper pitch. Nevertheless many fine instruments do have problems with wolf tones. Often players can tame it by placing a few grams of mass on a string between the bridge and tailpiece in a position where the resonant frequency matches the wolf tone. The mass makes it harder for the string to interact with the resonance, which reduces the effect. Different string gauges sometimes help, and even different playing techniques can help. Sometimes wolf tones will seem to come and go with changes in humidity and so forth. This is simply due to the instrument’s resonant frequency changing slightly due to differing atmospheric conditions.