Wolf tone

A wolf tone, or simply a "wolf", is produced when a played note matches the natural resonating frequency of the body of a musical instrument, producing a sustaining sympathetic artificial overtone that amplifies and expands the frequencies of the original note, frequently accompanied by an oscillating beating (due to the uneven frequencies between the natural note and artificial overtone) which may be likened to the howling of the animal. A similar phenomenon is the wolf interval, usually between E flat and G sharp, of the various non-circulating temperaments.

tringed instruments

Wolf tones are usually only noticed on bowed instruments, most notably the cello and surrounding violin family, since the tones produced are played for much longer periods, and thus are easier to hear. Frequently, the wolf is present on or in between the pitch E and F.

A wolf can be eliminated with a piece of equipment called a wolf tone eliminator. This is a metal tube and mounting screw with an interior rubber sleeve that fits around the offending string below the bridge. Different placements of this tube along the string influences or eliminates the frequency at which the wolf occurs. It is essentially an attenuator that cuts down on reverberation.

An older device on cellos was a fifth string that could be tuned to the wolf frequency; fingering an octave above or below also attenuates the effect somewhat, as does the trick of squeezing with the knees.

Lou Harrison was said to have written a piece (evidently reworked as the second mvt. of the Suite for Cello and Harp)that exploited the wolf specific to Seymour Barab's new cello.

Brass instruments

Brass instruments use a standing wave of air which is amplified by the bore shape and bell flare to produce a note. The notes in the harmonic series are carefully tuned by the instrument designers, but most instruments will have some notes in the harmonic series which are slightly off pitch, and these are known as wolf tones.

Trumpet

There are various ways to tune wolf notes on the trumpet, the most common of which is the use of the first- and third-valve slides. Below is a list of wolf tones on the trumpet, their general tuning problem, and their respective remedies:

* Low C#: Very sharp. The player must push the third-valve slide out.
* Low D: Very sharp. The player must push the third-valve slide out, much like for the C#.
* Low E, Middle A: Slightly sharp. The player must push out the first valve slide about a centimeter.
* Middle D: Always flat. Pitch must be "lipped up" by the player; in other words, the player must buzz faster while still maintaining the note.
* Middle A: Somewhat sharp. First-valve slide may be pushed out slightly, but the alternate fingering of third valve may be used instead.
* High D: Slightly flat. Alternate fingering (no valves pressed) may be used.