I see that this popped up on HNQ, so I wanted to expand on shoover's excellent answer with a build showing one way that this could be put together for folks that may not be as familiar with LEGO elements as the Bricks community.
As was already pointed out, the key element here is the 2x2 turntable base without a turntable attached:
Here's how you might ...
The easiest way to do this would be to use a motor with a high speed (or gear up a lower speed motor) and then attach one of the larger propeller elements to it. You can probably build a custom prop, but it might be challenging to build something with the proper blade angle while keeping it light and strong enough to not break apart when rotating quickly.
From this picture and this one, you can see that the framing of the windows is formed by Turntable 2 x 2 Plate, Base in black.
For the colored areas (the "stained glass"), you have a couple of options:
You could use different "Trans-X" colored Plate, Round 1 x 1 inserted into the back, but you'll need some trans-clear plates to back them up so the ...
Donny Chen made a LEGO piano that I believe is just large enough to play. Details are available on LEGO Ideas. You can watch him show it off in a video from Brickvention 2019. He has it motorized in that video.
From your comments, it sounds like you are interested in not simply having a piano with keys that can move, but one that actually emits proper sound....
There is this monstrosity as an example on the internet, which proves that you can work with proper metal strings. But your biggest enemy will be the huge tension everything is under. There is a reason that proper pianos have steel frames. As you only want one or two octaves, you can probably do without reinforcing the frame, but wherever the strings ...
this way it can open and close
Blue = 4276 Hinge Plate 1 x 2 with 2 Fingers
Yellow = 4275 Hinge Plate 1 x 2 with 3 Fingers
LightBlue = Plate 2 x 4
White = Plate 2 x 2
Pink = Plate 1 x 4
Light Bluish Gray = Plate 1 x 3
Yellowish Green = Plate 1 x 2
Red = Tile 2 x 2
Green = Tile 1 x 4
There is a bit of a challenge with a geometry. LEGO doesn't produce much symmetrical hinges, otherwise they would be out of system. I could think of the following one piece you could achieve a close result - Hinge Plate 2 x 4 with Pin Hole and 3 Holes - Top. It comes in White color as well, so you could incorporate in your layer of white plates.
Here's a ...
Mmmh... If you base doesn't have to be all solid...
Recess some piece in there in which you can insert the arm-side of a mini-fig hand.
Grasp your swimmer by the toes on one of its feet, with that hand.
That will give you a horizontal/slightly upwards position on the mini-fig and you can further increase the angle by adjusting the mini-figs leg.
I think you missed step 273 on page 133 of book 1.
In this step you align the front and back wheel and move a gear wheel and bush so the front steering mechanism is connected to the rest.
To fix this you need to disassemble part of the front
After taken of the fenders
Follow steps 471 till 484 in reverse.
This removes the panel above the gear so you should ...
There are several pieces which can be attached to minifigures to pose them. Recently a line of collectible minifigures introduced a transparent "handle" with a single stud which could be connected to the feet or legs of the minifigure
This piece can be rotated in the anti-stud to angle whichever way is convenient, then held in place using a hole ...