Graph Tech ghost Acoustic MIDI System - Steel String PK-7077-00 is the Acoustic MIDI system for Steel string guitars. It allows you to add our Hexpander and Acousti-Phonic to any steel string guitar. Play the Impossible! Outfit your Bridge with the ghost modular pickup system (sold separately) Get studio quality acoustic tone or MIDI compatible output at the flick of a switch The Possibilities are ENDLESS with the Graph Tech GHOST Modular Pickup & Bridge system. Available At Ant Hill Music!