Pianos are weird.
The lowest notes, generally have one string that makes the note. The middle, have two strings (persumably to make it louder).
the high notes have 3 strings per note.
So sometimes playing one key is actually playing three tones.
Pictures from a violin/piano maintenance building school make it a little clearer: https://www.nbss.edu/full-time-programs/piano-technology/cur...
> This is why you hire a piano tuner to tune your piano.
Idk... I think it's more about the hassle. People I've known let their piano get really out of tune (like we are talking a quarter tone off for some tones "just avoid those"), to the point where their own amateurish tuning would be a big improvement, before they call the tuner over.
Actually, the way a piano is tuned is pretty funky.
The rigidity of the strings means the higher 'harmonics' of a note get sharper and sharper. If you tune the fundamentals to exact equal temperament a piano sounds out of tune, because the upper partials of lower notes are pretty sharp versus the lower partials of higher notes.
Hence the frequences of the fundamentals are stretched out such as to get the inharmonic partials as in tune sounding as possible between different notes.
This is why you hire a piano tuner to tune your piano.