The Major 7 and Dominant 7 Chords Explained

The difference between a Major 7 (Maj7) chord and a Dominant 7 (dom7) chord lies in the intervals that make up each chord.

1. Major 7 (Maj7) Chord: A Major 7 chord is built by combining a major triad (root, major third, perfect fifth) with a major seventh interval. In other words, it consists of the root, major third, perfect fifth, and major seventh of the corresponding major scale. For example, in the key of C, a C Major 7 chord would include the notes C, E, G, and B, since those are the root, major third, perfect fifth, and major seventh of the C major scale. The Major 7 chord has a bright and lush sound, often associated with jazz and sophisticated harmonies.
2. Dominant 7 (dom7) Chord: A Dominant 7 chord is built by combining a major triad (root, major third, perfect fifth) with a minor seventh interval. It consists of the root, major third, perfect fifth, and minor seventh of the corresponding major scale. For example, in the key of C, a C Dominant 7 chord would include the notes C, E, G, and B♭, since those are the root, major third, perfect fifth, and minor seventh of the C major scale. The Dominant 7 chord has a strong and tense sound, commonly used in blues, rock, and other genres.

In summary:

• Major 7 (Maj7) chord has a major triad with a major seventh interval, resulting in a rich and lush sound.
• Dominant 7 (dom7) chord has a major triad with a minor seventh interval, giving it a strong and tense sound.

It’s worth noting that in traditional functional harmony, the Dominant 7 chord often serves as a dominant function, resolving to the tonic chord, while the Major 7 chord is more often used for color and as a tonic or subdominant function. However, these chords can also be used creatively and outside of their traditional harmonic roles in various musical contexts.