the reeds inside a vintage accordion
(photo by Nathan McKnight from Wikipedia)
You might think that since the piano accordion has keys, that it is a percussion instrument like a piano. In a piano when you strike a key a hammer strikes a string. However, the accordion is a reed instrument. Yes, like a clarinet or oboe. The sound is produced by air passing over reeds inside the accordion box. The air is produced, not by blowing, but by the motion of the bellows.
The bellows are sealed. If you try to force them open or closed without pressing a key or button you can damage the instrument. (There is also an air button to release the air and safely close the bellows with no sound.) If there is a leak in the bellows you will get sound, but it will be hard to complete musical phrases with one push or pull of the bellows.
I know this is blowing your mind! I'll stop for today.