Concert pitch A440(A above middle C vibrating at 440 times per second)has been universally accepted as the pitch to which all instruments should be tuned. It ensures that when instruments play together, they will all be in tune with one another. Pianos are designed and built to sound their best when tuned to A440.
Every note on a piano is tuned using A-440 as the starting point. A-440 has been accepted as the universal standard for most of the century. Before that, it varied as much as a semi-tone higher or lower.
And even farther back in time, there was no standard at all. Every village used a prominent local instrument, such as a church organ, as the standard for tuning its musical instruments. Pity the wandering minstrel.
So when your piano's pitch drops due to lack of tuning, the quality of tones suffers. Also, if piano is not tuned for quite some time, its pitch begins to slip far enough away from concert pitch that it may require a pitch raise in order to achieve a stable tuning.
Concert pitch is very important for piano students!
What Does “A-440” Mean?
Sound occurs when air is set into motion rapidly. Humans can hear sound if those cycles of compression and uncompression occur anywhere from twenty times each second[20Hz] to about twenty thousand times each second[20Khz].
When a piano string is set into motion, it vibrates up and down repeatedly. If the note A above middle C is properly tuned, that string will vibrate 440 times in one second. That’s what A-440 means.
This is A440, press play button.