Today when I was playing the organ in church, I noticed it was just the least bit flat. Now if I were playing alone, that wouldn't be an issue. No one would notice. But I was playing with a piano, keyboard, bass, and acoustic guitar. When that many instruments figure into the mix, everything needs to be in tune to have the very best, most pleasing harmony. That little bit of flatness in the organ just put an edge on the morning's music. Unfortunately, I can't go up and tune the pipes, which probably wasn't the problem anyway, since the whole organ was flat. Maybe it was all the many nights of sub-freezing temperatures that affected it, maybe the air pressure from the bellows was below par (it's a pipe organ). Whatever it was, it couldn't be fixed. Now most people probably didn't even notice. But I did.
This same kind of silghtly-out-of-tuneness can also make the most beautiful piece of jewelry seem just not quite right. If the shade of a certain stone, the shape, the size, or even the kind of stone is not just quite right, everything seems the slightest bit out of harmony. So the blending of colors, shades, textures, shapes all goes into creating the most breathtaking work of art and gives the perfect harmony that will hopefully elicit that response that the creator wants from the prospective customer.