My piano goes out of tune right away after a tuning. Why does this happen?
There are three possible reasons for tuning instability:
Environmental changes can cause your piano to go out of tune. If you are not taking steps to control humidity, the tuning of your piano will change dramatically when you begin and end heating your home each year. This is far and away the most common cause of tuning instability. Please read the page on 'What makes a piano go out of tune' to learn more about why this happens and read about 'tuning stability and climate control' to learn more about what can be done.
There is a structural problem with your piano. Your piano technician should be able to diagnose a problem like this.
Your piano technician may be inexperienced. Tuning stability is one of the hallmarks of an experienced tuner. However, it is important to be sure it isn't one of the reasons listed above before blaming your piano technician.