Question: How do I determine the difference between major and minor chords?Antonia (Charlotte, North Carolina, USA)
Albert's reply: Major and minor chords are both triads. A triad consists of three notes, each of them a third above the previous. (This is the case when the chord is in closed position with the root of the chord on the bottom.)
That's a rather technical definition, so let's take it apart before moving on to major and minor chords. Let's take a C major triad as an example:
The root of the C major triad is, of course, C. Here, it's in the bass (i.e., the bottom note), so the chord is in root position.
The notes of a triad can be stacked in thirds, starting with the root. The note a third above the root is called the third of the chord, since the interval between the root and this note is a third.
The note a third above the third is called the fifth of the chord (they can't both be called the third!), since the interval between the root and this note is a fifth.
Thus, there are two thirds: between the root and the third of the chord, and between the third and the fifth of the chord.
Each of these thirds can be either major or minor. Because a third is an interval, the terms major and minor refer in this case to those intervals, not to the quality of the chord itself. (The various meanings of the terms major and minor are detailed in Distinguishing Minor from Major.)
As explained in Music Theory Intervals, we can recognize thirds purely visually on the staff:
Without even knowing which notes these are (because there is no clef), we can immediately see that this interval is a third. Any notes on adjacent lines or spaces on the staff are a third apart.
We don't know what kind of third this is—major or minor (or diminished or augmented, or even doubly diminished or augmented)—until we know the exact notes.
In our C major triad, we can immediately see that it consists of two stacked thirds, because the notes are all on adjacent lines:
Here is a C major chord on the piano:
Notice that E is four keys above C on the piano keyboard, while G is only three keys above E? This is the difference between a major and minor third.
A major triad (often called a major chord—triads are a type of chord) thus consists of a minor third on top of a major third.
A minor triad is the reverse: a major third on top of a minor third. Let's use C minor as an example:
Here, we can see that E-flat is three keys above C on the piano keyboard, while G is four keys above E-flat. We already knew that these particular notes, C to E-flat and E-flat to G, are thirds because of their positions on adjacent lines of the staff. Now we know that C to E-flat is a minor third while E-flat to G is a major third, making this a C minor triad.
To summarize, a major triad consists of a major third plus a minor third (going up from the root of the chord), while a minor triad consists of a minor third plus a major third.