Mordent
A mordent is a quick main-note, neighbor-note, main-note figure. It decorates one written pitch with a brief departure and return, rather than sustaining a long alternation.
- main-neighbor-main
- quick return
- direction depends on sign
How does it appear in notation?
A short wavy sign sits above the main note; some forms have a small vertical stroke. The direction and naming of “mordent” have not been entirely uniform across periods and editions. Check the actual form, nearby accidentals and the score's style before choosing the upper or lower neighbor.
Which note is the main one?
The normal-size notehead under the ornament is the anchor. If it is C, return to C after touching a neighbor. The neighbor normally comes from the key or a local accidental. Do not let the three fast notes add an extra beat; fit them into the written note's place in the rhythm.
How does it differ from a trill?
A Trill usually alternates repeatedly over a longer span. A mordent makes one compact excursion. Play C-D-C once, then keep alternating C-D several more times without changing the main beat. You can hear the boundary between the two ideas.
Practice the two directions
On each of four steady beats, play C-D-C on the first two and C-B-C on the next two. Keep each figure compact enough for the next beat to arrive on time. The difference between upper and lower is easier to remember once you have heard both.