Pythagorean harmonics. 15th-century artwork of an account of experiments on musical harmonics and the octave, said to have been carried out by 5th-century BC Ancient Greek philosopher Pythagoras. At upper left (labelled Jubal, a descendant of Cain and biblical father of music) he is listening to the sounds made by blacksmiths at work. At upper right he experiments with different ratios of bells and water-filled glasses. At lower left, stretched strings with different ratios are being plucked. At lower right, Pythagoras and his student Philolaus play pipes in various ratios. Woodcut from 'Theorica Musice' (1492) by Italian music theorist Franchinus Gaffurius (1451-1522).