Why pianos go out of tune.
Many factors cause pianos to go out of tune, particularly atmospheric changes. For instance, changes in humidity will affect the pitch of a piano; high humidity causes the sound board to swell, stretching the strings and causing the pitch to go sharp, while low humidity has the opposite effect. Changes in temperature can also affect the overall pitch of a piano. In newer pianos the strings gradually stretch and wooden parts compress, causing the piano to go flat, while in older pianos the tuning pins (that hold the strings in tune) can become loose and don’t hold the piano in tune as well. Frequent and hard playing can also cause a piano to go out of tune. For these reasons, I recommend that pianos be tuned once a year, or for frequently played pianos every six months.
Always keep old pianos away from dry heat such as radiators and warm centrally heated rooms, keeping a jar of water in the bottom of a piano can help, but putting it in a cooler room or near a kitchen or source of humidity is better. Having said this too much humidity is also to be avoided, a cool damp room can cause damp and mould can form in the workings of the action making the piano sluggish to play. A happy medium is the best option having considered all the above points!
Does moving a piano effect the tuning?
Moving a piano is to be avoided if possible. It generally doesn’t cause a problem as the strings are held with great pressure inside the frame. However it could send an upright piano out of tune if its moved on an uneven floor as this can twist the piano causing octaves to go out of tune. Grand pianos that need to be moved should be fitted with an ‘A’ frame under the legs to aid moving.