If there are different musical instruments tuned alike in one room ... when one is struck, the others have the tendency to vibrate so as to give the same note.

...

When I am doing a certain action, my mind may be said to be in a certain state of vibrations; all minds which are in similar circumstances will have the tendency to be affected by my mind.

Of course this influence of thought on mind will vary according to distance and other causes, but the mind is always open to affection.

Swami Vivekananda
Read the whole lecture here
(it makes more sense in context)