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→Sample Song in G Major
e----------------|---------------|--------0---2--|3--------------|
b-------------0--|1-------0---1--|3--------------|---------------|
g-0---0----2------|---------------|---------------|---------------|
d----------------|---------------|---------------|---------------|
a----------------|---------------|---------------|---------------|
Here is a very simple song using a I - IV - V - I progression in G Major. The chord progression is written above the tab. You can apply rhythm to it however you like, as discussed [[Applying Rhythm to Chords|in a prior lesson]]. The melody written in the tab basically just ascends the G Major scale, playing the root of the chord in the harmony on the downbeat of each measure.
Notice there's nothing special about the different keys. Notes may change and chords may need to be voiced a little differently, but ultimately what matters is the pattern. A I - IV - V - I progression will sound the same in G Major as it does in C Major. The ascending G Major scale melody above uses the following notes from the scale: 1 2 3 4 3 4 5 6 7 8. Using the same relationship of notes in C Major would produce an identical effect.
== Why Use Different Keys? ==
So if everything is relative and any major key is going to be roughly the same as any other major key, what's the point of using different keys? Why not write everything in C Major?
We have not yet gotten to the topic of [[Modulation|modulation]], which involves changing keys inside a song. This can have a profound effect on the piece as a whole. It requires we know all the keys used, which is at least 2. Modulating isn't always going to be to the current key's 5th, either. While one song may modulate from C Major to G Major, another song may modulate from C Major to E Major.
While many songs have sections devoted to a modulation, it doesn't need to be so obvious. We may want to modulate out of the key for just a measure to play a certain melody we think will sound good over the current chord.
Even if a song does not modulate to another key, it may require being written in a certain key so that it fits the range of a certain instrument. For instance, consider a piece written for clarinet, whose range is E3 to G6. The piece features an ascending 3 octave arpeggio run of the tonic chord, ending on the root note 3 octaves above the original note. There are only a few possible notes that this will work for without exceeding the clarinet's range: E, F, F# and G. If C Major is the key, the clarinet will not be able to play the piece. So the piece is written in a different key, such as E Major.
Even if an instrument's range is not the concern, timbre might be. For instance, many songs written for guitar are written in E Minor. Even though the guitar could play the song in any minor key, the composer chose E Minor because the low E is the lowest note of the guitar. He had hitting that low E in mind when he wrote the piece, which is deeper and more impactful than hitting the A or Eb above low E.
If a song is written in one key for a certain instrument, but we want to play it with a different instrument, we may consider ''transposing'' the song to a different key. This simply means moving all the pitches/notes uniformly higher or lower. All the relative pitches between notes remain intact. However, now the piece may fit the instrument's range or desired timbre. For guitar, the easiest way to do this is to use a capo. All the chord fingerings will be identical.