How to develop perfect pitch.

 A single tuning fork can be used to tune all 88 keys of a piano. Every note has a precise derivation from this single reference. To do this as a mental discipline, we must internalize the tuning fork. It is not the perfect 440-cycle "A" note that professional piano tuners use. It is different for everyone and is based on long-term memory formed before puberty and preferably before the age of four. There may have been a bell, a buzzer, a musical toy, or a popular song on the radio that can easily be recalled in memory. It is important to use something that is within a few cents of an actual musical halftone. If it is possible to re-experience it, do so. It is so much the better. Find the name of the tone, not just the pitch but the octave as well. Middle C begins the lowest note of the 4th octave and is identified as C4, B3 is a half step lower. You must try to recall the tone often and "test" it by playing the note you think it is. Many people can get within a whole tone of it on the first try. The exercise is to keep getting closer with each try. With a popular song, try to use an actual record played on an accurate machine. Some broadcasters adjusted speeds to fit timing schedules which affects pitch. Use a well tuned piano to identify your note. You can do this with other songs and starting notes. This will build a reference library in your head.