One way to approach playing minor 7th chords is by using the dominant 7th chord as a starting point. Let’s take a look at the C dominant 7th chord (for which the chord symbol is C7):
C E G Bb
If we simply take the third of the chord, which is E in this case, and lower it one half step, we arrive at:
C Eb G Bb
There you have a C minor 7th in its basic form. Chord symbols used for the minor 7th chord include:
Cm7 (note the lower case “m”)
Let’s take a look at the functionality of minor 7th chords as they relate to a given key. In the key of C Major, we can build a chord on each degree of the corresponding scale (C Major scale):
C E G B
D F A C
E G B D
F A C E
G B D F
A C E G
B D F A
Note that each of these chord tones conforms to the C Major scale. In other words, there are no chord tones that are not included in this scale. Therefore, these chords are said to be diatonic. In the diatonic system, we can see that we have three chords that are minor 7th chords in the key or C Major:
Dmin7 (the II chord)
Emin7 (the III chord)
Amin7 (the VI chord)
Since our musical system is mathematically perfect, each of the other major keys will also have three minor 7th chords… and, yes, the three chords that will be minor 7ths in any key will always be the II chord, III chord, and VI chord.
The diatonic system of chords is one that you will absolutely want to familiarize yourself with at deeper levels. Doing so will lead you to a much greater understanding of how music works. It will open all kinds of doors for you when it comes to gaining confidence with chord progressions within your tunes. Also, having a grip on the diatonic chords in various keys can also have you predicting what chord is likely to come next in a song even if you have never played it. This does take some familiarization, of course, but your time invested will be more than worth it. In addition, if you aspire to create your own music via writing your own songs and/or improvising, having a handle on diatonic chords will prove to be highly valuable to you!
PLAY WITH PASSION!