accentor
n.a person who adds a sharp, high note to a musical chord. This word is very old and is mostly used by music historians today.
n.a person who adds a sharp note to a musical chord, specifically the note a third above the base.
“The accentor added a high note to the choir's harmony.”
“In the 14th century, the accentor played a vital role in the development of polyphonic music by introducing these sharp intervals.”
“Scholars of medieval music often debate the exact role of the accentor, as the term appears primarily in theoretical treatises rather than surviving musical scores from the period.”
From Latin accentor (“one who sings with another”), from ad + cantor (“singer”), from canō (“sing”). Superficially accent + -or.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.