This is just to defer a discussion that began in the Religion forum concerning "https://www.physicsforums.com/showthread.php?s=&threadid=429&perpage=15&pagenumber=3" [Broken]. It seems there are two approaches: the seven note diatonic scale, i.e., do, re, mi, fa, so, la, ti, do, developed by Guido D'Arezzo around 1,000 years ago in tribute to Saint John; then there's the twelve note chromatic scale, which is apparently more common and currently in use today. Anyone care to put their two cents worth in here? .. It's a big debate over in the other forum.