I think from a budo viewpoint, aiki means to blend your spirit with the opponent's and dominate their spirit, intent, will, posture, etc. I have felt this done from some distance with just a look by senior budoka.
When combined with proper physical technique such as kuzushi, tsukuri, etc. you should be able to achieve control at first touch.
The word "harmony", in my understanding, means simply "good timing and fitting." Any moralistic or philosophical attitudes vary from person to person.
Some teachers have also taken the larger view to include "becoming one with the universe", etc.