The word “key” in music is kind of like the words “to”, “two”, and “too” in that they sometimes lead to confusing as to when to use which. A key signature tells the musician what sharps or flats are in a given song, and therefore it defines the key of the song. To be in a key means the piece of music is based on the scale of that key.
For example, a key signature with 4 flats — B, E, A, and D — indicates that the song is either in the key of Ab or it’s relative minor key, F minor. A key signature of 2 sharps — F and C — indicate that the piece is in the key of D or its relative minor key, B minor, and therefore uses the notes of the D scale in its formation.
So each key signature announced to the performer the scale of the key in which the song is written.
Key signatures are a type of musical notation that indicate which key the song is to be played in. But key signatures, despite the name, are not the same thing as key. Key signatures are simply notational devices; just as a note is the notational name for a pitch, key signatures are the notational names for keys. It is what it says it is: a signature, a simple piece of information that tips you off to the physical form (the key) to be played.
Key signatures appear right after the clef (before the time signature) and show a sharp or flat on the line or space corresponding to the note to be altered. Key signatures placed at the beginning of songs will carry through the entire song, unless other key signatures are noted after a double bar, canceling out the first. For instance, it’s entirely possible to start a song in the key of F but end it in the key of E flat; it all depends on the key signatures and where they’re placed throughout the song (a key signature can change at any point). Accidentals can also show up throughout a song and only once or twice flatten or sharpen a note that was not previously indicated; this cancels out the key signatures, as well, but only temporarily, for as long as the accidental lasts.
Beginners just learning to read music often have a hard time with key signatures because the key itself is not expressly written, and it’s sometimes difficult to remember what goes where. Key signatures with five flats or sharps have been known to terrorize new musicians — how in the world, they think, are we supposed to remember all these note changes while we’re playing the song? It’s obviously possible, though, and there are some rules that can help beginners identify and remember the key as it relates to the key signatures, rules that go beyond rote memorization. If there is more than one flat, the key is the note on the second to last flat. If there are any sharps at all, the key is a half step up from the last one noted. F major, a key frequently found in beginning sheet music, only has one flat (B), and C major has no sharps or flats at all. Key signatures, when viewed in light of these rules, are much easier for beginners to digest, ensuring that a proper knowledge of key signatures is on its way through the door.
Piano keys, on the other hand, are the physical keys – the 7 “white notes” and the 5 “black notes” – on a keyboard. Which piano keys are played in any given song depend on the key signature of the song, and therefore what key the song is in.
No wonder beginners sometimes scratch their heads!
Piano programs for beginners are at Piano Courses For Beginners & Near Beginners