Audio: vibrato (0:03)

Figure: vibrato

vibrato plays a vibrato sound effect simulating the sound of a UFO flying overhead. Frequency Modulation is used to create the vibrato. The carrier is a sine wave with a frequency of a 220Hz and the modulator is another sine wave with a frequency of 6Hz. The modulator cannot be heard, its purpose is to make the frequency of the carrier wobble six times a second. A high modulation index of eight produces lots of sidebands which add depth to the timbre of the sound. The vibrato figure shows the waveform. The amplitude of the vibrato is enveloped in two linear segments, a fast fade-in and a long fade-out.

Vibrato is a regular and repetitive change of pitch.

Vibrato is a frequency processing technique that does not rely on filtering. One way to achieve a vibrato effect is to use Frequency Modulation (FM), as shown in vibrato. The frequency of the modulator determines the rate of vibrato. A 6Hz modulator makes the frequency wobble six times a second, a 3-4Hz vibrato produces a gentler wobble effect. The depth of the pitch variation is determined by the modulation index: a high index of 8 adds lots of sidebands to the sound, a low index of 2 will produce a purer sound.

Vibrato is often used to mimic the natural vibration present in a human voice or a musical instrument. A vibrato rate in the region of 4-8Hz adds realism and warmth to singing and to the sound of stringed instruments.

Vibrato can also be used as a standalone sound effect. A high rate of vibrato will produce all sorts of vibrating and wobbling sound effects.

Vibrato and tremolo are often mixed up. Vibrato is a change in frequency, tremolo is a change in amplitude. Guitarists are totally confused because the tremolo arm on a guitar is a misnomer and should be called a vibrato arm.