That’s an easy one (though it may not be easy to hear the answer), and the answer is borne out by my 28 years tuning pianos in Oakland County (Oak Park, Southfield, West Bloomfield.. ) and the greater Detroit area.
Your piano must be tuned every year. Not tuning your piano in a timely fashion will cost you time and money, and can lead to much more costly repairs. Here’s why:
A piano’s strings (wires, really) are under tremendous tension. As time passes the wires stretch and the tension decreases. This makes for a piano with flat notes.
If the piano has not been tuned in over 10 to 15 years the entire piano can go a half step or more flat. This is what we call “really not in tune.” Almost grating to the ear.
When the piano gets to this point, it becomes necessary to do a “pitch raise,” each and every string on the piano must be raised to where it is supposed to be.
So at this stage of “piano neglect,” if the pitch is raised to correct pitch, the wires will continue to stretch, and the notes will fall a bit flat once again. That is why if the piano hasn’t been tuned in a very long time, it is not possible to fine tune it without first raising the pitch of all the strings above correct.
After one or even two of these tuning treatments and after the piano’s contents have adjusted and settled for a couple of weeks, it is possible to finally fine tune the piano – in most cases.
If your piano is tuned to pitch every year, a pitch raise will never be necessary, and the piano can be fine-tuned at the first appointment. This will result in less cost and less hassle, and your piano will sound beautiful all the time!