From MusiCAD

A mordent (indicated by mordent or a prall prall with a line through it) is a similar decoration as a pralltriller. The difference is that a mordent uses the note below the note to decorate. You use the keyboard shortcut <m> or the trill menu to enter.

mordent-playing in different tempi

Depending on tempo, a mordent is played differently as given above two possibilities. A mordent will be played according to the ornamentation settings (slow/fast, diatonic/chromatic, baroque).

See also