For day 11 in this year's Blogging A-to-Z challenge, we take a look at keys. Not the ones on a musical instrument, but the ones on a staff sheet.
A key designates which scale the piece (or part of the piece) uses to establish its tonality. In this year's very first A-to-Z post, I showed you the four principal scales (major, natural minor, harmonic minor, and melodic minor) that Western music uses most of the time. In that post, you may have noticed that the major scale had the notes C through C without any accidentals (sharps or flats), but the three minor scales all had flats in several places. That means the major scale was in the key of C major, and the minor scales were all in the key of C minor.
To avoid writing all those accidentals throughout the score, we can use a key signature, that essentially says "these sharps or flats run from here to the end (or the next time we change keys)." For example, here again is the C major scale:
And here again is the C natural minor scale, but this time with the proper key signature:
Also remember how every key has a relative key? That's easy to see with key signatures. Here's the A natural minor scale; note that its key signature is the same as its relative key, C major:
Though I might get some argument from some modern composers, generally you can have no more than 7 sharps or flats in a key signature. Each sharp or flat on a key signature takes the key up a fifth in what we call the "circle of fifths." Take a look at how that works. Here are the keys with flats in their signatures:
Start with C; up a fifth to G, up a fifth to D, etc. Now the flat side:
Start with C; but this time, down a fifth to F, down a fifth to Bb, etc. So it works the same way as sharps, but in the other direction.
Often pieces will change keys mid-stream; this is called a modulation. Here's a simple example from Bach in which he modulates several times, between C minor and its relative key, Eb major, with a clever modulation to F minor for a couple of bars. And here's a lampshaded example from Beethoven. (Listen to the whole Schickele clip. The first time I heard it I almost pissed myself laughing.)
Tonight is the Apollo Chorus annual benefit and cabaret, which I'm co-chairing, so tomorrow's A-to-Z might be slightly delayed.