 To use a string as an example, it will simultaneously vibrate the full length of the string (fundamental), with a nodal point in the middle (double frequency—one octave higher), with two nodal points dividing the string in three (triple frequency—one octave and a fifth higher), with three nodal points dividing the string in four (quadruple frequency—two octaves higher), four nodal points dividing the string in five (quintuple frequency—two octaves and a major third higher) etc.Just intonation involves reproducing these exact pitches so that the resulting combination of frequencies resonate sympathetically, and the intervals have a stability and "ring" to the sound that results from this resonance.Instruments are not always tuned using these intervals.