Audio effects such as vibrato, tremolo and phasing are examples. Guitarists often use the terms "vibrato" and "tremolo" misleadingly. Christgau also noted Shakira's strong vibrato and constant changing of timbre in her vocals. A player can use this to create a vibrato or a portamento effect. Stefani avoids the heavy vocal vibrato that she often uses. Instruments without a vibrato have other bridge and tailpiece systems. The warble can be approximated by use of vibrato techniques. Surf and early rock instrumental guitar is synonymous with vibrato use. The ES-355 was available with a Vibrola vibrato unit or a Bigsby vibrato tailpiece. Lynch's use of a bottleneck resulted in guitar sounds featuring excessive vibrato. Mancuso plays a Yamaha Revstar 720B equipped with a Bigsby Vibrato and 2 VT5 humbuckers. She sings without vibrato, a pulsating musical effect used to add expression. Her vibrato, her cadence, her control. It features Plant's voice fed through a vibrato amplifier. The TransTrem provided the functionality of a capo in addition to vibrato effects.