It was a stringed instrument used to study musical concords and the mathematical relations that define them.
It consisted of a square wooden soundbox, four parallel strings of equal thickness and length which were stretched by equal metal weights and a diagonal bridge (which went from the start of the first string through to the middle of the fourth). The four strings with the two tailpieces formed a perfect square with the second string going through its middle and the third going through the intersecting point of its diagonal and its bridge. Thus resulting in the vibrating string lengths with the ratios 3, 4, 6,8,12, yielding, with safety, the notes MI, LA, mi, si, mi΄ making the helikon a reliable “tuning” instrument of antiquity.
Its name derived from Mount Helikon, the mythical dwelling of the Muses.