Tuesday, February 3, 2009

Finding the Right Voice – How We Hear Vibrato

The vibrato pit. That’s the image that sprang to mind during a recent choral rehearsal. I was glad I was sitting in the end seat in my row, so that at least one side of me was a vibrato-free zone. The singer to my left sang with a fast narrow vibrato, just slightly under pitch. The singer immediately behind me sang with a slow, wide vibrato, “hanging” her sound significantly under the pitch. (I’ll explain that in a moment.) And behind me, a whole cloud of varying vibrati buzzed and burbled. Together, these voices created a sort of choral chaos which made it hard for me to hear the center of the pitch.

The issue of vibrato in choral singing has always been of interest to me, perhaps because I’ve sung so much early music where vibrato is seldom used, and because I’ve sung in choirs (Gaudeamus and CitySingers of Hartford) where vibrato ist verboten.

What is vocal vibrato, anyway?

Vibrato, pronounced vih-brah'-toh, means “vibrated” in Italian. It’s the “wavy” or pulsating quality that is heard in most trained voices (and in many untrained voices, too). Properly produced, vibrato can lend warmth, color, and intensity, and even a shimmer, to a singer’s tone. Used appropriately, vibrato can be an attractive ornament in the singer’s repertoire.

Note the emphasis here on properly produced and employed appropriately, meaning 1) technically correct and 2) musically appropriate. In this essay, I’ll offer my perspective on the technical (auditory) aspects; in my next essay, I'll discuss the place of vibrato in choral singing.

As would be expected, individual singers display remarkable variation in the production of vibrato. Properly produced, vibrato is a controlled, rapid, oscillation of pitch centered on a core tone:

Vibrato can also incorporate rapid fluctuations of timbre and/or intensity. These subtle oscillations are more noticeable in loud singing than in softer singing.

Vibrato can be slow or fast (this referring to the number of “beats” per second, that is, speed):

In most singers, vibrato occurs at 5-7 oscillations per second.

Vibrato can also be narrow or wide (this referring to degree to which the pitch varies above and below the central note, that is, amplitude):

In most singers, amplitude typically covers +/- 3% (+/- .5 semitone).

To my ears, amplitude is generally determined by the general voice type and weight; larger voices tend to have wider vibrato; smaller voices tend to have narrower vibrato. Speed is often a function of amplitude (larger voices have slower vibrato), but it can also be controlled by some singers, to varying degrees.

In employing vibrato, many singers focus on speed and amplitude and fail to consider the placement of the vibrato relative to the core or central pitch. In many cases where a singer’s vibrato is unattractive or distracting, it is due to inaccuracy of pitch, particularly flatting (placing the core pitch too low). The vibrato must surround and embrace the core or central pitch; that is, the high and low extremes of amplitude must be exactly equidistant above and below the central pitch:

Too many singers “hang” the vibrato on the core pitch, so that the overall tone reaches the correct pitch only at the top of the vibrato wave:

Thus, even though the upper part of the tone touches on the correct pitch, the overall effect is a flat (under-pitch) tone, because the ear perceives the overall pitch as the point midway between the extremes of oscillation. This is true whether the vibrato is fast, slow, narrow, or wide.

Some singers will add vibrato to conceal under-pitch singing, thinking that the steady fluctuations in pitch will camouflage the flat central tone. It doesn’t work; it just makes the situation worse. Discerning listeners will always listen for the central or core pitch, and no amount of vibrato can hide it. In fact, listeners with good pitch sensitivity will hear the flat central pitch and the high and low points of the vibrato, which are also flat.

We’re used to hearing vibrato in trained solo singers. Does it have a place in choral singing? That’s the topic of my next essay. You can read it here.

To read all my essays on my experiences as a chorister, including more on technique, click here: http://quodlibet-sarah.blogspot.com/search/label/Chorister

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