The experienced piano owner will have probably found out some of the following from long term ownership, but these few tips may be of help to the beginner.
There are optimum times of the year for tuning pianos. One should avoid the height of summer when the humidity is at its greatest. The soundboard will absorb excess moisture in the air during the summer and the pitch will invariably rise.
In the depths of winter when the air is drier the soundboard will be suffering in a different way, this is when the pitch of the piano is likely to fall. Try to avoid having your piano tuned on a very cold day. When the frost lingers all day and the temperature is low, the first thing to go up is the heating thermostat, this further dries out the air making the piano feel even worse. The best time of year for tuning is from early to mid September - through to late November early December.
The spring tuning session is anything from February through to late June. Piano tuners work better when it is not freezing cold and not blindingly hot. Think of your piano, think of your tuner.
The temperature and relative humidity to the air are most important to the well being of your piano. In reality it is difficult to counter against the effects of what is happening outside but you can help your piano at difficult times of the year.
A digital hygrometer is very useful to accurately calculate your relative humidity. In the winter you will see this drop into the 30 - 40% region, for a precious vintage instrument this is too low. Ideally you should try to keep your relative humidity no lower than 50% and no higher than 75%. At certain times of the year this will be impossible unless you have a sophisticated humidity control system.
If you have a humidifier expect to pour a considerable amount of water into it if you are to redress the balance from say 35% to 55%. Try and circulate the air in the room when it is very dry, keeping copious quantities of plants in the room can help in the winter, but don't over do it in the summer.
As far as temperature is concerned it is important that you the pianist feel comfortable, trying to play Chopin Etudes with fingerless gloves and an overcoat on is not a happy mix, have the heating on in the winter but again - don't over do it - think of your piano.
Don't let it get there is the answer to that!
On a grand piano it is essential to keep it clean inside. When not in use you should always keep the lid down and the half lid closed over. All those piles of music placed on the half lid might be handy for you, but your piano is taking in dust every day if left like that. Dust that gathers by the tuning pins, by the string bearing felts, by the dampers - its all very harmful to the long term health of the piano.
Your tuner should be encouraged to blow the dust out from your piano on every visit, ask him or her to do this.
I have a lovely story to tell about cleaning out a grand piano. I was puffing away at clods of dust with my hand operated bellows, a good deal of it was going over the bemused owner standing by the keyboard, when the comment was made "are you actually putting that dust into my piano?!"
So remember, keep the lid down and the half lid closed when not using the piano and have it regularly cleaned out, think of your piano.
This is a problem with ivory key coverings and moisture from ones hands.
A clean soft cloth should be used to carefully wipe down the key coverings, be careful when working in between the sharps as excess pressure on these keys could stress the key bushings. If the keys are really dirty you should use a slightly damp cloth to clean them first and finish off with a dry cloth.
The Yamaha ivorite key coverings must be kept clean or discolouring can take place in later years. Ivory key coverings will also discolour if kept in the dark or if left dirty. If you have ivory key coverings always leave the fall board open. Every now and then there will be no option but to have your technician take care of a service to the key frame and keys. At this stage the keys can be buffed and the build up of grease removed from the sharps.
A thoughtful technician will also stain in the sides of the sharps where the fingers over the years break through the black stain. If you have an ivory key covering come off, try to get it glued down again as quickly as possible before a build up a grease discolours the original glue fixing. For the best results in re gluing ivory key coverings the work should be carried out by an experienced technician.
To some extend this a personal matter, but we can look at the serious 'do not' cases.
Good light on the keyboard is desirable, but possibly not if this is south facing and will attract the sun at its hottest. At all costs you must avoid any part of the casework heating up due to exposure from the sun. In time this will destroy your tuning stability, possibly cause damage to the timbers and almost certainly cause bleaching of the veneers if your piano is in a mahogany case.
Try to reach a balance of light, position and appeal. Having a grand positioned so that the lid opens directly into a wall is not ideal, if nothing else you will find it difficult to lift the lid (no bad thing if you don't intend to close it). If there is no option but to have it in a window where the sun will fall on it at certain times of the day, it is clear that you must be prepared to pull the curtains or blinds over when this happens. Fine if you remember, but disaster if you don't and then go away for a week in the summer!
If the piano must be close enough to a radiator or heat source you should consider the making and use of a protective guard to stop the transfer of heat to the piano. Looking after your piano in this respect will pay dividends in later years.
There can be many reasons why a piano drifts out of tune. With older unrestored pianos it could be that the tuning pin torque is not sufficiently tight to over come the pull of the string tension. There is little one can do about this other than consider having over sized replacement tuning pins fitted, this is most commonly done when restringing the piano.
Other reasons could be continually changing humidity or more seriously a poor fit between the plate and the pin block. For a piano to stand in tune well it is clearly necessary for the whole construction to be firm. If the strings are old and age tempered then getting the string to cooperate with the tuner is a well know problem. Leaving the string in equal tension between the pin, the agraffe or capo bar and the hitch pin is a tuners nightmare with old strings. In cases like this the less winding up and down the better as it will often be impossible to recapture some form of stability in the tuning.
The hallmark of an experienced tuner here is his sensitive approach to every individual piano. If the piano is quite new you will also find there is a period of seasoning, perhaps over some two or three years, before the tuning becomes more reliable. Try to keep the pitch sharp when the piano is new, long periods of not having a new piano tuned, followed by considerable pitch raising are hardy conducive to stability.
If your piano design has the use of a capo 'dastro bar in the top two sections, it is possible at some stage in the pianos life to experience string breakage under the bar.
As the strings age the upward pull of the string cuts into the bar and in time they can become weak at this point. If the hammer heads also become string cut and flat on the nose due to excessive use of the una corda pedal you have the recipe for continual string breakage. By putting one replacement on is only a short term answer as naturally enough the string goes back into the small cut in the bar. Without removing a section of strings it is difficult to clean the bar and therefore protect against further string breakage.
Some pianos will go a life time with out breaking strings, others seem to break strings just by looking at them. Clearly if this is the case one must look deeper into the design and construction and consider the longer term effects of this. Restringing of the top two sections is a straight forward enough procedure by the experienced technician and when completed can give a new lease of life to a singing treble - but beware - the tuning stability is dire for a period, so try to plan in advance a good time to have this work done. Having the top two sections restrung one day and expecting it to stay in tune for Beethoven's fourth piano concerto the next is not what the strings or piano had in mind.