Topic summary
Equal temperament
Equal temperament is a musical temperament (tuning system) that divides the octave into 12 identical parts. It is a logarithmic scale with a ratio equal to the 12th root of 2 ( ≈ 1.05946). The scale unit is known as a semitone or half step.
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Twelve-tone equal temperament (12 TET) is the most widespread system in music today. It has been the predominant tuning system of Western music, starting with classical music, since the 18th century. It has also been used in other cultures.
In modern times, equal temperament is usually tuned relative to a standard pitch of 440 Hz. Over the past few centuries, standard pitch has risen significantly.