Plato described astronomy and music as "twinned" studies of sensual recognition: astronomy for the eyes, music for the ears, and both requiring knowledge of numerical proportions.
[4] Later philosophers retained the close association between astronomy, optics, music and astrology, including Ptolemy, who wrote influential texts on all these topics.
[5] Alkindi, in the 9th century, developed Ptolemy's ideas in
De Aspectibus which explores many points of relevance to astrology and the use of planetary aspects.
[6]