singing a simple harmony

Singing harmony can be as simple as singing a three note bass line.  In today's lesson I will show you how to do this with the song "Skip to My Lou".  The chord progression goes back and forth between the I and V chords.  Since the I and V chords share one tone ("so" or D in the key of G major), you could sing this note throughout the song and be singing harmony, but this would get monotonous and you would not get the feel of the chord changing.  A better way to do the bass line is to use the common tone and then add another tone from the chord as it changes.