I am currently playing in a baroque group. The question has arisen as to how long an appoggiatura should be in triple or compound meters.
According to Wikipedia (https://en.wikipedia.org/wiki/Appoggiatura),
The time subtracted is generally half the time value of the principal note, though in simple triple or compound meters, for example, it might receive two thirds of the time.
Is there a "rule" as to when it should receive one third of the time, and when two thirds?