We are hitching the string on the piano.
The word "String" refers the one with copper winding.
The word "Wire" refers the one without it.
Tension on each string or wire is over 80Kg.
This high Tension makes each strings and wires stretching.
The reason why Brand New piano goes out of tune in fast
is in this graph by Master Tuner and Technician, James Shin.
Basically If you don't tune your piano over 2 year after stabilized.
( Stabilized means usually 3 years after Manufactured Date)
The stability go back to around -50cent and it makes more money and time
to get the proper stability again.
(See how pitch desperatly fall down right after 1st tuning.
It happens again if you don't tune your piano atleast once in an year.)
Also it effect piano's structual condition badly.
For as the string/wire stretching it changes integral tension on the frame
and soundboard.
There's around 200 strings/wires in the piano.
10Kg tension change on each strings and wires make the soundboard
and frame's tension 2 Ton totally.