I found myself playing Burgmuller's Arabesque quite "uneven" (so to speak). I mean the ABCDE part that then moves to DEFGA and so on. I sounds very easy to play, I know, but it can turn out to be a little complicated to syncronize it with the staccato chords on the left hand at high speeds.
The thing is, I started to practice just that particular movement of the hand for a few minutes, to notice that my fingers were unnecessarily tight, so I just relaxed them. Along with this, I noticed that this "half scale" sounded a lot better, or more "flowing" if I played it a little more horizontally, I mean, not pressing the keys at an angle so near to 90º, but rather 45º or so. Then I took it to the extreme to see what happened and played it with my hand wide open, with my fingers completely horizontal, pressing the keys with the whole finger and not just the tip. I know this will sound absurd to all of you, and you must probably be thinking "this guy doesn't know what he's doing", but let me tell you, it sounded pretty good.
Now, I know most passages simply can't be played like this for obvious reasons (I can't picture myself doing a hand crossing like this), but let me ask: what is, if any, the general rule regarding the angle of the fingers? Is it 90, 45, as you please, as you feel right, as sounds best or what?
Topic: Finger "angle"