Tuned just for Shirley 88 to A-440 concert pitch.
Q: What is concert pitch?
A: Concert Pitch is usually referred to as A-440. The A is the A above middle C, and the 440 is a measure of frequency of vibration. Put it together and the A above middle C in a concert pitched piano will vibrate exactly 440 times per second. All other notes are mathematically derived from this reference pitch. When all strings are tuned to their predetermined frequency the whole piano is “at concert pitch”.
The American Standards Association recommended that the A above middle C be tuned to 440 Hz. This standard was taken up by the International Organization for Standardization in 1955 and has served as the audio frequency reference for the calibration of acoustic equipment and the tuning of pianos, violins, and other musical instruments.