<Li> al - Ḥasan ibn Aḥmad ibn' Ali al - Kātib, author of Kamāl adab al Ghinā' ("The Perfection of Musical Knowledge"), copied in 1225 (Istanbul, Topkapi Museum, Ms 1727). </Li> <Li> Safi al - Din al - Urmawi (1216 - 1294 CE), author of the Kitabu al - Adwār ("Treatise of musical cycles") and ar - Risālah aš - Šarafiyyah ("Epistle to Šaraf"). </Li> <Li> Mubārak Šāh, commentator of Safi al - Din's Kitāb al - Adwār (British Museum, Ms 823). </Li> <Li> Anon . LXI, Anonymous commentary on Safi al - Din's Kitāb al - Adwār . </Li>

Which is not one of the basic elements of music