In music, a chop chord is a, "clipped backbeat." In 4/4: 1 2 3 4. It is a muted chord that marks the off-beats or upbeats. As a rhythm guitar and mandolin technique, it is accomplished though chucking, in which the chord is muted by lifting the fretting fingers immediately after strumming, producing a percussive effect. The chop is analogous to a snare drum beat and keeps the rhythm together and moving. It's one of the innovations bluegrass inventor Bill Monroe pioneered, and it gave the music a harder groove and separated it from old-time and mountain music.— Bruce Dix