The harmonic type indicates natural and artificial harmonics. Allowing the type of pitch to be specified, combined with controls for appearance/playback differences, allows both the notation and the sound to be represented. Artificial harmonics can add a notated touching pitch; artificial pinch harmonics will usually not notate a touching pitch. The attributes for the harmonic element refer to the use of the circular harmonic symbol, typically but not always used with natural harmonics.
The
<harmonic>element.The harmonic type indicates natural and artificial harmonics. Allowing the type of pitch to be specified, combined with controls for appearance/playback differences, allows both the notation and the sound to be represented. Artificial harmonics can add a notated touching pitch; artificial pinch harmonics will usually not notate a touching pitch. The attributes for the harmonic element refer to the use of the circular harmonic symbol, typically but not always used with natural harmonics.
See
https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/harmonic/