Art Piano - The Lyre Logo

In Ancient Greece, certain musical tribes used a lyre, a four-stringed harp called the tetrachordon (tetra meaning four).  The four tones encompassed by this instrument constituted a perfect 4th, and were called a tetrachord.  This was the building block that was to become the basis for our modern scales.

The Greek philosopher Pythagoras (around 500 BC) is credited with the discovery of the numerical ratios corresponding to the principal intervals of the musical scale.  With an instrument known as a monochord, consisting of one string stretched over a long sounding-board, Pythagoras found that by dividing the string into 2 equal parts, one part, when vibrated, would give a tone exactly one octave above the natural tone of the whole string.  By sounding 1/3 of the length of the string, the interval of a 5th above the natural tone would be produced.  By sounding 3/4 of the length of the string, the interval of a 4th would be produced.  In this manner, the ratios of all the notes of the scale were discovered.  This was accomplished by the use of a moveable bridge which was positioned according to these calibrations.

---excerpted from The Complete Book of Scales, Chords, Arpeggios and Cadences by Palmer, Manus and Lethco (Alfred Publishing, 1994)