At some point we have to deal with the issue of what is in these chords we are playing and why do we play them when we do in music. So here is where we start the conversation and lay out some chord construction theory and the idea of substitution.
First lets look at the major building block of harmony and that is the Major scale:
When we build chords we create what are know as triads. Triads are 3 note chords that are based on the Major scale. We simply start stacking notes on top of each other by the interval (distance) of a third. In practical terms you place notes on the next line or space based on where your first note is located. (see example)
When we play the triads in a Major scale, these are the qualities (major, minor diminished) of the resulting chords:
When we spell the notes of the chords they look like this:
C= C, E, G
Dm= D, F, A
Em= E, G, B
F= F, A, C
G= G, B, D
Am= A, C, E
Bdim= B, D, F
When you see the notes of the chords, you can hopefully see some relationships that connect them.
For instance, a C chord has the notes C, E, G while the Am chord has the notes A, C, E. These chords have two notes in common and one that is only a step away. These chords are often substituted for each other. It is a great way to vary the sound of what you are playing and sometimes inspires new ideas and new approaches to a chord progression or a song. Here are a list of some of our basic chords and chords that can sometimes work as substitutes. Keep in mind that your ear will ultimately tell you whether the chord works or not as a substitute.
Chord Possible Substitutions
C Am, Em
F Dm, Am
G Em, Bm
D F#m, Bm
E G#m, C#m
A C#m, F#m
This relationship works inversely as well. You can substitute C for Am as easily as you can substitute Am for C. This can sometime be helpful when working on a song. Having trouble with that pesky C#m chord? Try an E chord and see if you are satisfied with the sound.