What is A=440? Why is this important?

440 Cycles per second is the conventional frequency assigned to "A" of the piano scale. This is what you hear when you play "A" natural above middle "C".--That is if your piano has been recently tuned to match this standard. When a piano is left untuned and neglected, it will not only begin to sound sour within its own relative pitch, but will fall flat from the standard A=440cps. In this sad situation, when one plays "A" above middle "C" they are likely to hear "A flat" or an even lower note. This not only contradicts the rest of the musical world but can be a two fold detriment to piano enjoyment. First, it compromises the player's ability to develop a good sense of correct pitch, and second, the piano itself was designed to perform at its tonal best when proper string tension is maintained.
Pitch raising is the job the piano tuner must undertake in order to restore the neglected piano to the correct string tension. It generally involves several rough tunings prior to attempting any fine tuning. The recently "pitch raised" piano will require time and several more fine tunings before normal tuning stability is fully restored.