Vibrato
Vibrato is a periodic modulation of the pitch of a sustained tone, typically a few cycles per second. It gives a sung or played tone its characteristic warmth and is one of the things singers and instrumentalists train deliberately. Vibrato is described along two largely independent axes: its rate (how fast the modulation cycles) and its extent (how wide the pitch swing is).
Rate and Extent
- Rate
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The number of vibrato cycles per second, measured in Hz. Most classical singing vibrato falls between 5 and 7 Hz. Faster than about 8 Hz is usually heard as nervous or unstable; slower than about 4 Hz tends to be heard as a wobble.
- Extent
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The peak-to-peak depth of the pitch swing, usually expressed in cents or in semitones. Typical operatic vibrato has a peak-to-peak extent in the range of about 50 to 150 cents — between a half and one and a half semitones of total swing. Smaller extents read as a "straight tone with shimmer"; larger extents become hard to identify as a single pitch at all.
A given singer’s vibrato is not a single number: rate and extent vary with pitch, dynamic, and vowel, and they often become more consistent as a singer’s training matures.
Vibrato vs. Tremolo and Wobble
Vibrato is a pitch modulation. A periodic intensity modulation, with the pitch held constant, is called a tremolo. Many singers produce a small amount of tremolo as a side effect of vibrato; some instruments (organ tremulant, Leslie speaker, the violin technique called tremolo) produce one but not the other. Wobble is the colloquial term for vibrato that has become too slow, too wide, or too irregular to read as a single pitch — the line between expressive vibrato and unwanted wobble is largely a matter of context and taste.
Reading Vibrato in the Display
Vibrato is one of the easiest features to spot on a Spectrogram. The harmonics of the held tone, normally drawn as horizontal lines, instead trace gentle wavy lines that all move up and down in lockstep. Higher harmonics show a larger vertical excursion than lower ones — not because the vibrato is wider there, but because a given percentage swing in frequency translates to a larger absolute number of Hz at higher frequencies. On a logarithmic frequency axis the wavy lines run parallel.
The pitch line of the analyzer follows the same modulation, which makes the rate and extent measurable directly: the rate is the inverse of the period of the wave, and the extent is its peak-to-peak amplitude.
In VoceVista
The dedicated Vibrato View in VoceVista Pro shows vibrato rate and extent as continuous traces over time, separated from the underlying pitch contour. This is the easiest way to compare vibrato characteristics across phrases, sections, or singers.