In this column, I wanted to share some personal thoughts on something that seems pretty basic: Why do singers sometimes sing out of tune? There are a number of reasons that this may occur, even in singers who are well trained and musically sophisticated.
Can I preface this by saying that, right or wrong, these are only my own conclusions as a laryngologist, and I welcome any suggestions from singers and voice teachers, who know more about this than I do. One of the best perks of my profession is that I constantly learn from my patients.
It is assumed that a singer, whether professional or avid amateur, is musical. That is to say, they can distinguish tones and intervals and can reproduce them vocally. Pitch matching is a pretty basic requirement if one wants to be a singer—or, really, a musician of any sort.
But step back for a minute and consider how the voice is different from other instruments. Some instruments—such as the piano, harp, and some wind instruments—provide a series of fixed pitches. Other instruments—such as the non-fretted strings, other winds and, of course, the human voice—have no fixed pitch. The performer must re-create every pitch every time, choosing from a seemingly endless series of options.
In this sense, instruments (including the voice) can be classified into two groups, either digital or analog. On digital instruments (such as the piano), the pitches are predetermined: you either hit the correct note or not. You’re right or you’re wrong. On the violin, however, the sound you make can be anywhere, hopefully in the range of “correct,” depending on finger position, bow pressure, etc. If a pianist plays out of tune, it’s time to call the piano tuner. If, however, the singer sings out of tune, she and her teacher need to figure out why that is happening.
Also consider that singing may be a solo activity. Unless you’re singing with a piano or orchestra, there is no ongoing pitch comparison except for an internal one, your memory of the correct pitch, and of the previous notes just sung. And the quality (harmonic spectrum) of a piano or orchestra is quite different from a human voice. So, while comparing the sound of the voice with a piano or orchestra is not exactly comparing apples and oranges, it is at least comparing a Granny Smith and a Golden Delicious! Singers performing a cappella, such as in vocal quartets, are familiar with the difficulties of being unable to rely on a fixed pitch accompaniment, just as string quartets are.
There are other differences that affect a singer’s pitch sense vs. that of an instrumentalist. A violinist tunes his instrument carefully and then, while playing, relies on a combination of air-conducted sound, which travels from the instrument to his ears, as well as finger position and muscle memory in his fingers. But these latter are not acoustic phenomena.
The singer, on the other hand, monitors pitch by air conduction (the voice travelling from the mouth and around to the ears), but also bone conduction (resonance in the chest, mask, or head), two different acoustic cues, in addition to muscle position and proprioception (the mechanical appreciation of vibrations in the vocal tract). All of this information is then coordinated in the brain, measured against other sounds (like the piano or other instruments in the ensemble) and the singer’s own pitch memory (absolute or relative)—and, miracle of miracles, the voice comes out on pitch and in tune. The brain stores a set of variables (sound, vibratory sensation, muscle position, lung pressure) specific for each sound. This is why a singer (or a violinist, for that matter) can just begin with a specific pitch and doesn’t have to “find it” every time.
So, what about singing out of tune? There is obviously a tiny pitch range that is “correct” for each sound, and the note must land within that range to sound right. Small variations are acceptable and can be used musically, such as sharpening a seventh slightly or flattening a second, to lead to the tonic. Jazz musicians often “bend” a pitch on purpose. In singing, the obvious example of a vibrato also produces a range of pitches centering around the correct pitch. But when the variation is too great or lacks a tonal center, or when the ear perceives too great a distance between the sound expected and the sound produced, out-of-tune singing results.
There are situations when a note (especially at the end) is simply too high, and the singer is unable to reach it. This may be a technical problem, which may have an anatomic basis. The tightness and elasticity of the vocal folds, the muscular strength and control required to produce the proper laryngeal configuration, and possibly the shape of the resonators may be involved. These are the parameters that control the pitch of the voice. There is, after all, a reason why one singer can sing Olympia, another Sarastro. And of course with age, singers often lose some top notes they had earlier, as vocal folds become atrophic and less pliable.
On the other hand, we sometimes hear great singers in their prime, fully capable and with solid technique, sing flat. I believe the reason for this may be overblowing the larynx by using too much air. A telling analogy is a string instrument such as a violin or cello. If the cellist digs in the bow and pulls it very firmly across the string, he deforms the string and changes its length and vibratory characteristics, altering the pitch. Similarly, a reed player can overblow his clarinet or saxophone and change the pitch of the note. Singing softly is not always an answer, if the dynamics require a loud sound or if the singer needs to muscle the voice to get that high pitch out.
OK, but what about those who sing sharp? This is certainly not a lack of ability to hit a high note. Rather, I believe, it has to do with relying more on bone-conducted sound and vibration sense to place the note. The performance situation may be such (like in a loud orchestral tutti section or singing loudly with an ensemble) that a singer cannot hear the air-conducted sound of her voice and needs to use alternate stratagems to monitor the pitch.
Singing only (or mainly) by bone conduction and proprioception is a bit like instrument-guided flying for a pilot. Bone-conducted hearing is not as good as air-conducted hearing. One problem with bone-conduction sound is that high-pitched sounds have a shorter wavelength and don’t travel through the skull as easily as low-frequency sounds. There is a damping effect when sound enters another medium (in this case, going from air to solid, such as the soft tissues and bones of the skull). Although we teach medical students that sound travels across the skull bone to both ears freely, without any loss of energy (expressed in the audiological statement “interaural attenuation for bone-conducted sound is zero”), this is not quite so. Experimental studies (by Dr. Richard Goode and coworkers) have shown that above 700 Hz, bone conduction drops off progressively as the pitch rises.
I believe the singer simply doesn’t hear the high frequencies, whether fundamental or harmonics, via bone conduction as well as through air and needs to rely more and more on the physical vibration sense as the pitch rises. And the feeling of vibration, or the memory of position sense (which, for example, tells a pianist how wide to open the hand and where to place it to hit an octave), is not as reliable a guide for singers as air conduction of sound to the ear. Feeling, rather than hearing, the pitch can lead to over-singing, and the pitch becomes sharp.
Hearing the pitch of the voice is further compromised if the singer is in a situation where her ears are further distracted by competing sounds (such as in choral or operatic ensemble singing), and the need to rely on these internal guides for pitch becomes greater. Listening to competing sounds while trying to produce one’s own on-pitch vocal line is an example of cross-modality masking.
I would like to end this column on an up note. Pitch issues are complex, having to do with issues both in the control and outside the control of a singer. They relate in part to changing of the voice as it develops, learning technically to coordinate the multiple modalities of information reaching the brain about the sound being produced and developing the ability to use that information in the feedback loop back to the vocal tract.
These are all within the singer’s abilities to manage—and staying vocally healthy, working with a good teacher, and being aware of your instrument’s changing capabilities over the years are some obvious suggestions.
