I hear this question from beginning students all of the time:
What Is the Difference Between Major and Minor?
The difference between major and minor chords and scales boils down to a difference of one essential note the third.
The third is what gives major-sounding scales and chords their brighter, cheerier sound, and what gives minor scales and chords their darker, sadder sound.
What Do You Mean by Third?
If you’ve spent any time studying a few scales you should know many scales contain seven different notes. For example, the major scale contains a Root, 2nd, 3rd, 4th, 5th, 6th, and 7th.
Similarly, most chords and arpeggios usually contain 3 or 4 different notes like a Root, 3rd, and 5th (triads), or a Root, 3rd, 5th, and 7th (seventh chords).
All of these scales and chords contain that important note the 3rd in them. Compared to major scales and chords, minor scales and chords have different 3rds.
How Are the Thirds Different?
If you’ve studied the basic intervals that are the building blocks of all scale and chord patterns, you should remember there were two types of thirds major thirds and minor thirds. A minor 3rd is one note lower than a major 3rd.
Here is an example of a major 3rd (C to E) and a minor 3rd (C to Eb) [Click the play button on the diagrams to hear them.]:
All major-sounding scales and chords contain major 3rds while all minor-sounding scales and chords contain minor 3rds.
Understanding “Flatted” Thirds
To flat a note means to lower it by one note. Since the minor third is always one note lower than the major third, we often describe the minor third as a flatted 3rd.
That does not mean the minor 3rd must be spelled with a flat letter name. For example, these intervals all form minor thirds: A to C, A# to C#, D to F, C to Eb, Bb to Db, and many others. A flat third can be spelled with any letter of the musical alphabet whether its a natural note name, flat note name, or sharp note name.
Remember, it’s the distance between the notes that forms the interval and its unique sound. (Please review intervals if you are still confused on this. Intervals are essential to understanding scale and chord construction.)
Let’s compare a few examples of major and minor scales and chords:
The Difference Between the Major and Natural Minor Scale
An A Major Scale is spelled: A B C# D E F# G# (A).
An A Natural Minor Scale is spelled: A B C D E F G (A).
Notice the third of the major scale (C#) is one note lower in the minor scale (C). Again, flatting the third makes the scale’s third a minor third interval instead of a major third. This gives them their major and minor sound qualities.
You will notice there are actually three different notes between a major scale and a natural minor scale which start on the same note (compare the diagrams above). While there are 3 different notes, the essential note giving these scales their major or minor sound quality is the 3rd. As you continue studying scales you will learn there are many different major-sounding scales (e.g. Major, Major Pentatonic, Mixolydian, Lydian) and many different minor-sounding scales (e.g. Natural Minor, Harmonic Minor, Melodic Minor, Minor Pentatonic). Regardless of what other notes differ, it is the 3rd that gives a scale its "major-ness" or "minor-ness".
The Difference Between Major and Minor Chords
A C Major Triad is spelled: C E G.
A C Minor Triad is spelled: C Eb G.
Notice the third of the minor triad is one note lower, or “flatted” as we musicians say. Flatting the 3rd creates a minor 3rd interval giving the minor triad its minor sound.
Don’t Overextend Your New Knowledge of Major and Minor
Don’t start thinking that minor-type scales only contain minor intervals and major-type scales only have major intervals. That’s not strictly true. It’s the third that sets major and minor apart. The other intervals that build scales and chords can and will be a mixture of major, minor, and perfect intervals.
For instance, remember the dominant 7th chord? It contained a major 3rd, perfect 5th, and minor 7th. Despite having a minor 7th, this chord has a major-sounding quality to it because it has a major 3rd.
Summarizing the Difference Between Major and Minor
Major-type scales and chords contain major 3rds. Minor-type scales and chords have minor 3rds (a.k.a. flatted 3rds).
As you learn various scales and chord patterns on your instrument, pay particular attention to each pattern's third. You will soon recognize the difference between 3rds and flat 3rds and the sound of major versus minor.