Hearing harmonically is entirely different from hearing lines contrapuntally. In order to form a true harmony tones must converge with the same note values and the same articulations so that their vibrations may blend for a sufficient number of cycles to allow the essence of the chord to establish and clarify itself.
Linear hearing, on the contrary, is in constant flux; whatever momentary stases occur must not interrupt the flow and may even have to be slightly "out of tune" in order to affirm the fleeting nature of that texture.
We are not conventionally taught to recognize the difference. Especially not if we play the piano. Therefore our articulation is sloppy, our releases non-existent, our sense of line woefully inadequate to the genius of, say, Beethoven, or Mozart -- two composers we do not even think of as contrapuntal.
Try once counting the number of actual chords (as defined in the first paragraph above) in a movement by either of those two masters. I pretty much guarantee you will be shocked. Then make sure when you play that movement that you respect the difference between the one kind of hearing, which tends to be sluggish, and the other, which is anything but.
