Btw. Somewhere along my learning path I came across a video that showed a trick I didn't understand or think much of when I viewed the video. I forgot to bookmark video so can't find back to it.

Then thing I think was the take away was that for songs that linger on one chord for several bars they used the triad shape up or down 1 whole step to create some movement rather then static one chord. It became almost melodic.

In a blues I know I can slide in "from behind" and that works fine. But I usually slide a half step. Here it was whole step and not sliding but "swapping" back andforth between the new imposed chord and the underlaying chord.

I couldn't understand why that would work, nor when is the apropriate time to use it or what is available chords to impose over the one static chord underneath. It this understandable? I barely understand it and language barrier on top makes it hard to express myself.

Why does this work and why does it sound good? Is the answer to that in the scales?