主しゅ音おんしゅおんMeanings1nountonic; keynotemusicIn music theory, the first note of a scale, which serves as the tonal center.ハ長ちょう調ちょうの主しゅ音おんはドです。The tonic of C major is C.曲きょくの最さい後ごは主しゅ音おんで終おわることが多おおい。A piece often ends on the tonic.