plainchant

Plainchant or plainsong, the traditional monodic chant of the Catholic Church, still uses a four-line stave, and in earlier music the number of lines used varied.

素乐素——教堂传统单，依旧采用四线谱，早期乐中，线的数目各不相同。

Noteheads may be black (a circular or oval shape filled in) or white and are used on the staff to indicate pitch. The shape of noteheads has differed historically, as in plainchant.

符头可以是黑色的（圆形卵形）白色的，用在五线谱上以表明高。符头的形状在历史上有很多种，比如在单中。