The oldest record of this discipline's Daseian notation is a ninth-century anonymous treatise released in conjunction with Scolia Enchiriadis. This discipline has been in decline since the death of Cipriano de Rore according to a book titled for its ancient and modern forms by Vincenzo Galilei. A treatise on this discipline framed as a dialogue involving the student Aloysius [Al-OO-ish-us] introduced the (15[1])"species" form of one technique. Micrologus, a treatise on this discipline, introduced a mnemonic derived from (*) Ut Queant Laxis. Johann Fux's treatise on a part discipline is titled Gradus ad Parnassum. The "Guidonian hand" was used to memorize this discipline's system of hexachords via solfege. For 10 points, name this discipline that used polyphony in the Renaissance, which involves independent parts for multiple singers. ■END■