Trill
A trill is a rapid alternation between a main note and a nearby auxiliary note. The score may mark it with tr, a wavy line, or both. The main note tells you where the ornament belongs; the key signature helps determine the neighbor.
- main note
- nearby upper note
- repeated alternation
Which pitches are involved?
A common modern reading alternates the written note with the step above it. If the main note is C, the upper note may be D or D flat depending on key signature and accidentals. The sign gives the action, but surrounding notation settles the exact pitches.
Where does the trill end?
The wavy line, if present, shows its span. Some scores also notate an ending figure. Historical style can affect whether the ornament starts on the main note or the upper note and how it closes. For a first reading, keep the written beat in view and use the clearest neighboring pitch indicated by the score.
Trill or mordent?
A Mordent is usually a brief main-neighbor-main gesture. A trill repeats the alternation over more of the main note's time. Play C-D-C once, then C-D-C-D-C-D-C over the same beat to hear the difference.
Start slowly
Tap the pulse with one hand and alternate two notes with the other. If the alternation speeds up so much that the pulse disappears, slow the trill. A readable ornament should fit the phrase it decorates.