Common Tones

One of the many reasons why music flows so smoothly together is the use of common tones. Take for example the following: Pick the Key of C. The Tonic chord is comprised of the notes C E and G. Two of these notes also belong to the minor third triad in the key of C. They are the notes E and G. The minor third in its root position is E G B. This forms an E Minor chord. Dropping the C note down to a B note while leaving the E and G note still being played creates a 2nd inversion E Minor chord, B E G.
Another chord formed from the Tonic C E G, is the relative minor chord in the Key of C, called the A Minor chord. This is comprised of the notes A C and E. So from a C chord in its Tonic root position C E G, raising the G note to an A note creates a 1st inversion A Minor chord.
Take the Sub Dominant chord in the Key of C, the F chord, comprised of the notes F A and C. What could we do with this chord? How about going to an A minor? To do this, we would simply drop the F note to an E note. This would create a 2nd inversion A Minor chord: E A C.
I'll post more of these beautiful chords later. In the meantime, experiment.