Now let your eyes drift slowly upward, and you should see a flight of stairs going up and to the left. Below the stairs you will see a single bar like a piano key, and if you let your eyes drift up and around the stairs (don't climb them yet) you will see a pair of piano keys.
Go back to the fusion bars, then go left, past the single piano key to the left edge of the picture. Now the stairs appear to be coming up from below. Now slowly walk your eyes down the stairs, waiting on each tread until the image is well fused. When you get to the lower level, check out the piano keys. You will now see two below and four (!) above.
Go back up the stairs, or drop out of the image and come in again at the fusion bars. Now walk up the stairs. When you get to the top you will now see a cliff on your left. Walk over to the top and you will see a single piano key, and another cliff.
Try to figure out how to get 3, 5, 6, or 8 piano keys. Have fun.