Ptolemy [Klaudios Ptolemaios; Claudius Ptolemaeus]
- Lukas Richter
[Klaudios Ptolemaios; Claudius Ptolemaeus]
(b ?Ptolemais, after 83 ce; d 161 ce). Greek mathematician, geographer, astronomer and music theorist. He probably had access to an observatory at Alexandria, where he spent his working life. His major work, on mathematics and astronomy, was the Almagest (Arabic, al-majistī; Ptolemy's original title was Mathēmatikē suntaxis); a compendium of the work of earlier Greek astronomers, it describes a geocentric universe.
His three-volume Harmonics (Harmonika), written during the mid-2nd century, constitutes the most learned and lucid exposition of music theory in antiquity, its logical, systematic comprehensiveness making it a ‘worthy counterpart’ to the Almagest (Düring). In it Ptolemy discusses the principles and purposes of the theory of harmonics (i.1–2); the principles of acoustics (i.3–4); the theory of intervals, with a critique of the theory of the Pythagorean and Aristoxenian schools (i.5–11); the theory of the genera, with a critique of various divisions of the tetrachord (i.12–ii.1); a description of the helicon (a geometrical instrument devised, like the monochord, for measuring interval ratios using stretched strings; ii.2); the theory of 4th, 5th and octave species (ii.3); the Perfect System (...