Al-Farabi is one of the greatest philosophers in Middle Eastern history. The polychord can reproduce tone systems in their proper modal/performance context, as opposed to the out of modal context abstract monochord. Qanun is the Arabized word for the Greek kanon, which was a polychord of eight or 15 strings and used as an instrument to study the laws of acoustics and to reproduce the modes auditively. The instrument was used for "synthesis" purposes that are to compare notes of known ratios and to reproduce a tone system. The instrument as it stands is a far better tool to study the medieval Islamic tone system and acoustics than the ud because it reduces the variables of tone production to one only, that is, the string length. The ud is more complex because the student has to contend with tension variables applied to the various strings, and also the density variables, as the strings are of different thickness and different material.