I still don't understand what the proper way is to playing trills and tremolos, even though I've read a lot about them and watched a lot of videos. Worse it seems like all the people explaining it do them differently.
What confuses me is the movement of the forearm. I don't understand if the movement for a 2-4 trill or an octave tremolo solely comes from the forearm, meaning no movement of the finger muscles at all or if the movement comes from the finger with a little forearm rotation.
If I use only forearm rotation (the way I would rotate a door knob or change a light bulb), then I get extremly slow and watching other pianist doing tremolos or trills, it seems to me that the movemet comes from the finger and there is very little forearm rotation.
The second thing which I don't understand is the movement of the wrist. Especially when I trill on 2-4 and keep my wrist in motion then it feels very awkward to play a trill.
I know there are many questions about trills, but I still don't understand it after reading them.