It’s all in the wrist. Maybe not ALL, but certainly, a harpist’s use of the wrist is an important feature of technique.
Normally, I believe the wrist should be steady. When you play a scale, for instance, your wrist shouldn’t flex in and out to accommodate your fingers. Instead, it should be part of the support system for your hand. Your arm, starting with your shoulder, through your upper arm and down to your wrist, should be stable so that your fingers can play with certainty and place with accuracy.
NOTE: A healthy ergonomic position for your wrist is slightly bent inward at a natural-feeling angle. Keeping your wrist flexed at too great an angle can lead to injuries and carpal tunnel syndrome!
One wrist technique we harpists use is to “throw back” our hands by bending back at the wrists. This is most often used with a two-hand trill. I have heard it described as “plucking a chicken,” as your hands move quickly toward and away from the strings. The purpose of this technique is to keep the hands loose without moving too far away from the strings. It enables you to play rapidly and stay relaxed, and makes a clear and clean sound.
The other essential wrist technique is oscillation. Oscillation is easier to describe than it is to execute, especially at first. It is not an in-and-out movement like the one I described above. It is a back-to-front motion, a twisting motion much like turning a doorknob. Oscillation is used in one-hand trills or in patterns that alternate between any finger and the thumb. When you play the thumb, you let your wrist do the work, “turning the doorknob” away from you toward the column of the harp. The physical benefit of oscillation is that your wrist helps your thumb play. Your thumb doesn’t tire because your wrist is doing most of the work.
Oscillation is truly worth the time it takes to make it part of your technique arsenal. Henriette Renié describes it in Lesson 10 of her Complete Method for the Harp. Salzedo incorporates oscillation practice into exercises 7 and 9 of the Conditioning Exercises, as well as exercises I, VIa and b, and VIII of The Harpist’s Daily Dozen.
And don’t think that just because you don’t play trills, you won’t need it. Two pieces that have passages where oscillating can make the difference between playing with ease or struggling: Nataliana by Deborah Henson-Conant for the right hand, and Sonatina in Classic Style by Samuel Pratt (or any piece that uses an Alberti bass!) for the left hand.