wolf tone

wolf tone, phenomenon of resonance typically heard in bowed stringed instruments, particularly the cello, in which the vibrational frequency of a string being played and the fundamental vibrational frequency of the body of the instrument are very similar. The two vibrational frequencies interact to generate an undesirable beating tone, essentially the result of two notes very close in pitch being played simultaneously. In severe instances, the wolf tone fully replaces the sound of the intended note and is heard as a sort of trilling, wobbling, or stuttering sound sometimes likened to the howl of a wolf.

In the cello, the wolf tone generally occurs between the pitches of E and F-sharp, being especially noticeable on the C string but also present in higher positions on the G string and in first position on the D string. Although especially common on the cello, wolf tones also tend to occur in the double bass, the viola, and, less noticeably, the violin. In the double bass, the wolf tone typically occurs around the pitch of G-sharp; in the viola, around B-flat or C; and in the violin, around B or B-flat. The wolf tone can also occur in the guitar. It can affect even stringed instruments that have been finely made and properly adjusted, ensuring that the bridge and the sound post are optimally fitted.

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The wolf tone can be reduced through the use of an on-string wolf tone eliminator; common types of eliminators range from a metal tube with a rubber liner and a thumbscrew to simply a slotted metal cylinder. The eliminator is placed on the portion of a string that stretches between the bridge and the tailpiece, specifically where the string’s resonant frequency exactly matches the resonant frequency of the wolf tone. The eliminator works by adding weight to the string, thereby slowing or hindering vibrations throughout the instrument, making it more difficult for the string vibrations to interact with vibrations in the instrument body. However, in the process of impeding the wolf tone, the eliminator inherently filters resonant frequencies and potentially dampens the instrument’s overall sound. These effects may be avoided through the use of a magnetic modulator, which changes the vibrations in the top of the instrument to enhance sound rather than dampen it, or through alternative means for reducing the wolf tone, such as by adjusting the playing technique to attenuate vibrations in the body of the instrument.