Harping On

What gameplay is can vary.
According to the almighty Wikipedia, gameplay is ‘everything that the player experiences when playing the game’. Ergo, gameplay means…everything…
But there are a few different things we can go into detail about.
To me, gameplay always meant the control system or at least it’s what specifically sprang to mind but I agree that it is a multitude of factors.
Fable 2 has a system in place which will visually change the players appearance based what they do in the game, although it is still linear no matter how many choices you have to make.
Mirror’s Edge doesn’t require you to kill anyone and most of the time it persuades you to run away. First time playing this game on the second level you have to out run a SWAT team (again), I didn’t know the building and had about 3 seconds to get moving before screen went gray and I dropped to the floor. Because that’s what Faith (the character) does when she dies, and the only way to tell is to gage how desaturated her view becomes. I got my first adrenaline rush for years when playing that level, bolting over railings and down glass roofs. Which was a positive experience.
Rock Band is the other brother to Guitar Hero and has mostly identical controls, when I finally nailed Muse’s Hysteria to the point of 99% correct I felt like a rock god! I think this is down to the controls, when playing Rock Band on a standard gamepad it is nowhere near as fun and not half the experience.
I still find it hard to nail down what gameplay is.
I think it can be both incorporated and something unintended, but it changes based on what the game or genre is.