For string tremolo (3 slashes below note or on stem), why does Dorico frequently, but not always, put 4 slashes on the tied part of the note? I have tried changing to note to plain, then re-adding tremolo; does not work. I have tried shortening the note to the opening value, then re-lengthening; works occasionally. I would like Dorico to consistently use 3 slashes on each part of the tied note
Because usually the beam is included in the calculation.
When you enter a three-slash tremolo on an 8th note it’s actually a four-slash tremolo.
Before creating the tie, add the tremolo and force duration. Then when you add the tie, the 3 stroke tremolo will be retained on both notes.
When the tied chains are selected like in your screenshot, you can press UT (untie, tie)
As Vadian mentioned, the beam is included in the calculation of the speed of the tremolo. Each of the slashes represents one beam. The eighth note in your example has a beam plus three slashes which means the same thing as four slashes on the half note.
While having the same number of slashes would appear visually consistent, it’s actually incorrect musically. It would mean that the tremolo of the eighth note should be twice as fast as the tremolo of the half note.
Unless it’s for percussion, in which case the three slashes is standard on any note value for an unmetered roll.
While it’s common to do it that way, it’s certainly not universal. Many composers still adjust the number of slashes on an unmetered roll to allow for beams and flags.
Never seen that once in over 50 years, but I guess it’s possible.
Well, all I can say is, as a professional symphonic percussionist for more than 50 years, I saw it plenty of times.