Trill intervals tell performers which notes to play and also affect the pitches used in playback in Dorico Pro. For example, a trill with a sharp accidental on an E indicates that the performer trills between E and F♯, rather than between E and F.
If you do not specify an interval when inputting a trill, Dorico Pro calculates an appropriate interval based on the top note in the voice to which the trill belongs, the current key signature, and any accidentals earlier in the bar. For example, inputting a trill on an E♮ in C major produces a half-step/minor second trill interval to F♮. If there were a sharp accidental on the F earlier in the bar, the trill interval produced is a whole step/major second between the E♮ and F♯.
In open/atonal key signatures, Dorico Pro produces whole step/major second trill intervals by default.
You can specify trill intervals when inputting them with the popover, including at different noteheads in the same trill, and you can change individual trill intervals after they have been input. In 12-EDO, you can describe trill intervals based on their quality, such as major or minor.
When trill intervals do not require a trill interval indicator, they are indicated by signposts. However, trill interval signposts are hidden by default.
Trills and accidentals
If required, Dorico Pro shows accidentals to clarify trill intervals. Dorico Pro also automatically shows accidentals on other notes in the bar if they have different accidentals to any upper notes of trills.
By default, trill marks themselves show intervals, unless the upper note is modified by an accidental in the key signature. If the upper note has been modified by an accidental earlier in the bar, trills always show the interval. If trills modify pitches modified by an accidental in the key signature, any subsequent notes of that pitch show the appropriate accidental automatically. Any cautionary accidentals required in the current and following bars are also shown automatically.
Microtonal trill intervals
When using other tonality systems than 12-EDO, such as 24-EDO, you must specify trill intervals as an interval degree, expressed as the number of staff position steps, and total number of octave divisions from the notated pitch. This is because specifying only the interval quality is insufficient in such cases.