Understanding the rules of 5th in finding the matching chord

 

C Key and Its Relation to A Minor:

• The C major scale has no sharps or flats: C, D, E, F, G, A, B, C.
• A minor is the relative minor of C major, meaning it shares the same key signature (no sharps or flats) but starts on a different note (A instead of C).
• A minor chord is built off the note A. It uses the notes A, C, and E, and the C note is part of this chord, so A minor fits naturally within the C major scale.

Chords That Match the C Tone:

• C major chord: Built on the note C, it uses the notes C, E, and G.
• A minor chord (Am): Built on the note A, it uses the notes A, C, and E.

Both C major and A minor chords match because they both use the C note, and they fit within the C major scale.

The Meaning of the "5th" in Music Theory:

• The 5th refers to the interval between two notes that are five steps apart on the scale. For example:
  • From C, counting up five notes (C, D, E, F, G), you get G.
  • This makes G the 5th note in the C major scale.
• When you look at the circle of fifths, it’s a way of organizing key signatures in a circle based on this "5th" relationship. Moving clockwise in the circle means you’re adding sharps (or going up by fifths), and moving counterclockwise means you're adding flats (or going down by fifths).

In the case of C being your starting tone, if you follow the 5th rule, the next chord in the circle of fifths would be G major (since G is the 5th note from C).

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So in short:

• C is the root of C major, and A minor (Am) is the relative minor of C major, so both C major and A minor work with the C tone.
• The 5th is the distance of five notes between two pitches, and it's key to understanding chord progressions and key signatures.

Chords are formed by combining specific notes from a scale. Here's how you can understand chord formulation:

1. Choose a Root Note: This is the note the chord will be built on. For example, if you want to create a C major chord, the root note is C.

2. Determine the Scale: Chords are typically built from a particular scale. For a C major chord, you’ll use the C major scale: C, D, E, F, G, A, B.

3. Add the Third: The third is the note that is two steps above the root in the scale. For the C major chord, the third is E.

4. Add the Fifth: The fifth is the note that is four steps above the root in the scale. For C major, the fifth is G.

5. Optional – Add the Seventh or Other Notes: For more complex chords, you might add a seventh (which is five steps above the root) or even more notes like the ninth, eleventh, etc. For example, adding B to the C major chord would turn it into a Cmaj7 (C, E, G, B).

A basic formula for a major chord looks like this:

• Root + Major Third + Perfect Fifth (e.g., C, E, G for C major).

For a minor chord, the third is lowered by one half-step (one semitone), so for C minor, the notes would be C, E♭, and G.

There are many variations and extensions (like diminished, augmented, suspended chords), but the fundamental process is based on stacking intervals from a scale.