Now let’s look at strategies for building other chords. However, we will need to expand our knowledge of the keyboard. For instance, the C minor chord has one note which lies between two C major scale notes.
All Piano Notes Scale
All of the notes going from C to C with respects to the C major scale (red represents the C major scale notes):
C  (C # – D b) D  (D # – E b) E  F  (F # – G b) G  (G # – A b) A  (A # – B b) B , C 
Notice that the notes in parenthesis signify one note with two names. For instance, (C # – D b) refers to C sharp (represented by C #) and D flat (represented by D b). On the piano keyboard, those notes would be black, as opposed to the other ones (white).
Minor – 1 b 3 5
The Cm chord contains the 1, 3 b, and 5 notes. These notes correspond to C, (D # – E b), and E. Note: The 3 b would refer to the b of 3, or the flatted note before 3. Anyhow, our formula for finding C minor works because we are looking at the “All Piano Notes Scale” with respects to the C major scale (which contains the 1, 2, 3, 4, 5, 6, and 7 notes). We can deduce from this post that flatting the 3rd note of a major chord (1, 3, 5) makes a minor chord (1, b 3, 5).
Finally, before we end this post we need to understand the “Naming Formula”:
First of all, you need to make sure the target major scale (from which you would make your chord) has the same letter name as the chord.
For instance, if you want any type of C chord or scale then you build it via the C major scale. On the other hand, to build a G minor chord, you would look at a G major scale.
G Major Scale
Note: G major scale notes in red.
G  (G # – A b) A  (A # – B b) B  C  (C # – D b) D  (D # – E b) E  F (F # – G b ) G 
Of course, this isn’t written in stone, and isn’t the only way. Nonetheless, I think it’s the easiest way.
Anyhow, the G minor chord would be composed of the G, B b, and D notes