Here’s what some of the manufacturers say about tuning:
Steinway & Sons
… Unfortunately, no matter how expertly a piano is tuned, atmospheric variations, particularly humidity, and the nature of the piano’s construction constantly conspire to bring it off pitch.
Your Steinway piano has been designed and built so that in normal use and under normal conditions it should need only periodic tuning. We recommend that your tuner be called at least 3
or 4 times a year. You, however, are the final judge and should have the piano tuned as often as you think necessary. To put the matter of tuning into perspective, remember that a concert
piano is tuned before every performance and a piano in a professional recording studio, where it is in constant use, is tuned 3 or 4 times each week as a matter of course.
Tuning is an art practiced by skilled professionals and under no circumstances should anyone other than a professional be allowed to try to tune your Steinway piano.
Baldwin
In the first year, … have your piano tuned four times. This is a period of environmental adjustment for a new instrument and proper attention is important.
After the first year, the piano should be tuned at least twice each year depending upon the frequency of use and atmospheric conditions. … arrange for a reputable technician to service
your piano regularly.
Yamaha
Why schedule regular service? Having your piano serviced regularly is a lot like taking vitamins. As you regularly take vitamins, you generally feel better and you are able to perform at your
peak level. Also, taking vitamins helps you avoid serious illnesses and other health-related problems. The same is true regarding regular service for your piano. Regular service will keep your
piano’s performance (and your enjoyment) at its peak level. It will also correct “progressive” problems early, before they turn into costly repairs. For these reasons Yamaha strongly
recommends that you adopt a schedule of regular service for your piano.
… The strings need to be tuned a minimum of twice a year to restore them to their proper tension.
Bösendorfer
Climatic factors such as temperature or humidity changes may cause the precise tuning of your piano to vary. Also naturally over time the tuning will alter due to the tensions the strings are
constantly under.
If your piano receives normal use, we advise you to have your instrument tuned 2 or 3 times a year. Instruments which are being used more frequently, such as concert halls and recording studios,
are being tuned before each concert or recording session.
