Patent US 4,615,253

This invented device is a fingerboard key operated motor driven chording belt with a plurality of cams attached to it that are selectively lifted by electromagnet as the belt is driven and caused to ride between an elevated surface and cam wheel-push rod-rocker arm assemblies, and displace the rocker arms, to thus fret the adjacent strings and form any one of thirteen possible chromatic chords for use in playing a musical number on a guitar.