Piano keys and notes are not one and the same. There’s a difference. The keys are not really notes. They play notes, but are not actually notes.
Usually when talking about the notes or keys on a piano keyboard, a diagram like the following is used. The piano keyboard diagram below is labeled with the notes, A B C D E F G.
While in the diagram above the keys are labeled A B C D E F and G, these are not really the names of the keys. They just play these notes.
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Take the note to the immediate left of the set of two black keys for example. This key can play C but it can play other notes as well. It can play B sharp or even D double flat. In theory, this key can play an infinite number of notes. The key that plays D can also play C double sharp, E double flat or F triple flat.
When different notes corresponds to the same piano key, the notes are called enharmonic equivalents. For instance, F flat and E are enharmonic equivalents. G and F double sharp are enharmonic equivalents.
To put the labeling of piano keys into perspective, we need to understand what are sharps and flats. A sharp simply means to move up one semitone or half step on your piano keyboard. A flat means to move one semitone or half step lower on your piano keyboard. So since E is one semitone lower than F, it is the enhamonic equivalent of F flat. Since C is one semitone higher than B it is the enharmonic equivalent of B sharp. The name a note gets usually has to do with the choice of the composer. He may call a note a certain name to make it easier and more natural for the performer to read the music of a particular composition.
Here’s another diagram:
The black keys are also labeled here. Each black key has been labeled with two note names. These are the more common names, but as said earlier, the keys can play a limitless number of notes. The note that a piano key plays would depend on the key of the song. For example, if in the key of E, the second key in the set of three black keys would play G sharp, but if in the key of E flat, it would play A flat.
So we can clearly see that there’s a difference between notes and piano keys. Each key on the piano keyboard can represent several notes. Strictly speaking, the keys do not have names. Keys are not really called A B C D E F or G. They just play these notes. They can play other notes as well.
I highly recommend Piano For All to piano students.
For more information on this topic go to the main piano notes and keys page.