SYSTEM, in Music, signifies an exposition of all the sounds employed in composition, considered theoretically and practically, melodically and harmonically. The ancient Greek melodic system was divided into tetrachords; the modern melodic and harmonic system is divided into octaves. The Guidonian system was divided into hexachords. The most modern system of harmony, which originated in the sixteenth, seventeenth, and eighteenth centuries, is founded upon a system of tonality different from that em-
ployed prior to these periods, as will be shown under the article TONALITY. For some account of harmonic systems, see MUSIC.