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Lesson 19: KeysThis lesson explains what a musical key is. Keys are a basic music concept which you will need in order to understand both chord progressions and written music.
Before taking this lesson, you should know: major scales (Lesson 10: Major
In most songs, one particular pitch feels like the "resting" or "home" pitch; this pitch is the song's key. For example, if the pitch C feels like the home pitch, then the song is "in the key of C".
Keys can be major or minor. If a song's home pitch is C and most of the song's notes come from the C major scale, then we say the song is in the key of C major. If the song's notes come from a C minor scale, then the song is in the key of C minor.
Now let's see how you can play the same song in different keys. First, here is "Mary Had A Little Lamb" in the key of C major:
Click each note button above to hear the song.
Next, below, is "Mary Had A Little Lamb" again, this time in the key of E♭ major:
Again, click each note button.
Notice that when you play the song "Mary Had A Little Lamb" in a different key, all the pitches change, but the scale degrees stay the same. You can play "Mary" in any key by playing scale degrees 3-2-1-2-3-3-3 from that key's major scale.
Identifying a Song's Key
So, how do you tell what key a song is in (especially if it's your own song, or "fragment")?
Well, there's no "law" that says a song is "in a key" at all. A song (or fragment) is only "in a key" if it gives the listener enough musical clues for them to feel a home pitch.
Here are the common clues that make a song sound like it's in a key. Imagine a song that does these things:
If all of the above are true, then the song will probably sound like it's in the key of C (C major or C minor). You can take away or "weaken" some of the "rules" above and the song can still sound like it's in the key of C; in fact, many, maybe most, "real" songs will break or weaken some of these rules, because following them constantly can sound boring. But if you remove too many of them, then the song doesn't sound like it's "in a key" anymore.
You'll use keys to understand chord progressions, in Lesson 20: Roman Numeral Chords.