 A similar phenomenon is the beating produced by a wolf interval, which is usually the interval between E and G of the various non-circulating temperaments.Wolf tones are usually only noticed on bowed instruments, most notably the 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 pitches E and F on the cello, and around G on the double bass.