A wolf tone, wolf note, or simply “wolf”, is an undesirable phenomenon that occurs in certain bowed string instruments, most notably the cello. It occurs when the pitch — or more precisely the fundamental frequency — of the played note is close to a particularly strong natural resonant frequency of the vibration of the instrument’s body. Not infrequently, however, the phenomenon may also occur in wind instruments for similar reasons.A wolf note is hard for the player to control: instead of a solid note it tends to produce a thin “surface” sound, sometimes jumping to the octave of the intended note. In extreme cases, a “stuttering” or “warbling” sound is produced, as in the sound example given below. This sound may be likened to the howling of a wolf. A somewhat similar sound is the beating produced by a wolf interval, which is usually the interval between E♭ and G♯ of the various non-circulating temperaments. Frequently, the wolf is present on or in between the pitches E and F♯ on the cello, and around G♯ on the double bass.[5][6] A wolf can be reduced or eliminated with a piece of equipment called a wolf note eliminator. There are several types.