The A above middle C normally has a frequency of 440 cycles per second, or Hertz. This means that it vibrates 440 times per second. An A, one octave higher has a frequency of 880 Hz., exactly twice as many vibrations per second. The mathematical expression of this relation is 880:440 or 2:1. The following table shows the mathematical relationship of several intervals, ordered from consonant to dissonant.

Relation | Interval |
---|---|

2:1 | Octave |

3:2 | Fifth |

4:3 | Fourth |

5:4 | Major Third |

6:5 | Minor Third |

9:8 | Major Second |

16:15 | Minor Second |

See Intervals in the Tutorial section.

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José Rodríguez Alvira.