Disclaimer: I don't know music terminology, as I don't play any instruments.
The channel Sheet Music Boss on YouTube has two videos in which I've heard what I perceive to be two different techniques of some sort being played on a piano. I'd like to know if these techniques have any specific terms so that I can search for more, because it gives me goosebumps.
In the first video titled: IEVAN POLKKA (LOITUMA POLKKA) - Piano Tutorial at about 2:03 to 2:18 the music seem to change character, and becomes, for lack of a better term "magical". It looks to me as if the melody is still being played with the right hand, but something changed with the left I believe.
In the second video titled: When Johnny Comes Marching Home - Piano Tutorial at 0:57 to 1:20 it's pretty clear that the melody is being played with the left hand, while the right hand is playing what I assume would have been the bassline if it had been played with lower notes.