In this post, I will be covering the differences between a C7, Cm7 and Cmaj7 chord. Iwill choose the C chord because it has the easiest scale with no sharps or flats. Of course, you can apply the technique that I will be explaining to other chords as well.
First of all, we need to take a look at what the chords are called. As you would have guessed, a Cmaj7 is called "C major seven" and the Cm7 is called "C minor 7". How about C7? Well, the proper name to give it is actually "C dominant 7".
Now each of these 3 chords are played differently and I will attempt to explain how to play each of them.
In my previous posts about constructing a major and minor chord, we saw that the formula to take for a major chord is the 1st note, 3rd note, and the 5th note (1, 3 ,5). And, we saw that the formula to take for a minor chord is the 1st note, flat the 3rd note, and the 5th note (1, b3, 5).
Now, the formula for the major 7 is (1, 3, 5, 7) and the formula for the minor 7 is (1, b3, 5, b7). The formula for the dominant 7 is (1, 3, 5, b7). Remember these formula because you will use it when constructing a major 7, minor 7 and dominant 7 chord.
Now, let's take the C chord as the title of this post suggests. To play a Cmaj7 we would need 1, 3, 5, 7. The C major scale is C, D, E, F, G, A, B, C. Now we just have to simply count the 1st, 3rd, 5th and 7th note on the scale. That would give us C, E, G, B. Now, find these notes on your guitar. You will eventually find that one way to play a Cmaj7 chord would be like this:
From the diagram above, we can see that the chord satisfies all the notes that would make it a Cmaj7 chord.
Now, let's try the Cm7 chord. Applying the formula (1, b3, 5, b7), the notes needed for a Cm7 chord would be C, Eb, G, Bb. Try to find these notes on your guitar. You will find that one possible way of playing a Cm7 chord would be like this:
( A# = Bb / D# = Eb)
Notice the notes in the diagram above? They contain the notes needed for a Cm7. Therefore, this is one way of playing a Cm7 chord.
Lastly, the C7 chord. Let's apply the formula (1, 3, 5, b7) and see what we get. It would give you C, E, G, Bb. Likewise, let's find these notes on the guitar. You will find that a possible way to play C7 would be like this:
(A# = Bb)
So, there you go, now you know the difference between a major 7, minor 7 and dominant 7 chord. Remember, you can apply the formula to other chords as well. Have fun figuring out how to play these chords. What I showed above was only one way of playing a Cmaj7, Cm7 and C7 chord. There are many other ways to play those chords mentioned. If you have the time, try finding them out too.
So next time, when you see a song sheet which has major 7, minor 7 or dominant 7 chords in it, don't be afraid. You know exactly how to play them.