the horizontal movement of the arm/forearm is not a trick. (...)
The motion you describe is not a trick. It is one of the required movements that make the tremolos easy because the interval is not small enough that allows primarily the rotation of the forearm (unless you have unusually large hands) (...)
But being that necessary , why it is the first time I read something about this horizontal mvt when talking about tremolos? This shows that not everything is in internet...
I want to share a little trick I've found recently for using with the left hand tremolos of beethoven's Pathetique Sonata.
am surprised this thread got so many postiive responses, because it sounds all wrong to me! But perhaps I just dont understand what you are talking about. If you are moving your whole arm back and forth to play two notes which you can reach without moving your hand, you are surely wasting energy. Also, it is my view that in tremolos, even in articulate, measured ones, (where the "shaking" defintion comes less into play), the fingers should in fact be on the keys at all times. Perhaps you can explain this socalled horizontal movement in other terms. When I play a tremolo for instance from C to C, I notice my elbow is free, and there is a rotation movement which comes from the shoulder, but I cannot for the life of me imagine how you can effectively do this by moving all over the keyboard.