Just as notes are the rhythm symbol of melody, harmony marks are the rhythm symbol of harmony. Unfortunately, most traditional guitar and bass methods use a meter slash as the rhythm symbol of harmony. This is a fatal flaw. The only purpose of a meter slash is to make a beat visible, they do not help us in knowing what rhythm to play on that beat. For that to be known, harmony marks are needed!
Posted by Mike Overly 
12tonemusic 