Gretsch G9220 Bobtail Round-Neck Resonator GuitarGretsch G9220 Bobtail Round Neck Resonator Guitar Tone amplified! With its deluxe appointments and Fishman?? Nashville pickup, the Bobtail Round Neck stands out in the mix in more ways than one. The vital feature of all Gretsch resonator guitars is the Gretsch Ampli Sonic??? diaphragm (resonator cone), which is hand spun in Eastern Europe from nearly 99 percent pure aluminium, yielding an impressive quality and volume of tone.