Fishman Fluence Signature Series Greg Koch Gristle-Tone Pickup Set for Telecaster Guitars Voice 1  White-Guard. Open and airy, the sound of Nashville and Bakersfield, chicken pickin, and the big strum Voice 2  Black-Guard. Fat and punch, searing sustain. Undeniable Tele muscle Battery: Rechargeable battery pack Battery Life: Up to 250 hours