What is a Tone, a Semitone, etc.?
The musical interval between two adjacent notes in a partition of the octave into twelve (not necessarily equal) intervals is called a semitone; other names for it are a half step and a halftone. In the equal temperament, when the twelve intervals are equal, two notes are a semitone apart if the ratio between their frequencies is the 12th root of 2, or about 1.05946. A tone is the musical intervals between two notes that have exactly one other note between them, in a partition of the octave into twelve intervals. In the equal temperament, a tone is exactly twice a semitone, and two notes are therefore a tone apart if the ratio between their frequencies is the 6th root of 2 (which is the 12th root of 2, squared), or about 1.1225. Similarly, an octave is actually an interval of six tones, and a perfect fifth is an interval of three and a half tones – the frequencey 659.26, which is a perfect fifth above 440 in the equal temperament, is the seventh frequency after 440 in the frequency lis
