Vocal resonance may be defined as "the process by which the basic product of phonation is enhanced in timbre and/or intensity by the air-filled cavities through which it passes on its way to the outside air." Throughout the vocal literature, various terms related to resonation are used, including: amplification, filtering, enrichment, enlargement, improvement, intensification, and prolongation. Acoustic authorities would question many of these terms from a strictly scientific perspective. However, the main point to be drawn from these terms by a singer or speaker is that the result of resonation is to make a better sound, or at least suitable to a certain esthetical and practical domain.

The voice, like all acoustic instruments such as the guitar, trumpet, piano, or violin, has its own special chambers for resonating the tone. Once the tone is produced by the vibrating vocal cords, it vibrates in and through the open resonating ducts and chambers. Since the vocal tract is often associated with different regions of the body, different resonance chambers might be referred to as: chest, mouth, nose/"mask", or head^{[clarification needed]}.

In a more symbolic/perceptual way, rather than physical, the various terms applied can represent vocal "colors" in a continuous scale: from dark (chest) resonance to bright (head-nasal) resonance. We may call this spectrum a resonance track. In the lower range, the chest/dark color predominates; in the middle range, the mouth-nasal resonance is dominant; and in the higher range, the head-nasal resonance (bright color) predominates. The objective of using such images by several teachers and coaches is to achieve command of all the "colors of the spectrum". That, ultimately, may allow a greater scope of emotional expression. The emotional content of the lyric or phrase suggests the color and volume of the tone and is the personal choice of the artist.

There are some singers who are recognized by their pronounced nasal quality; whereas others are noted for their deep, dark, and chesty sound; and still others are noted for their breathy or heady sound; and so on. In part, such individuality depends on the structure of the singer's vocal instrument, that is, the inherent shape and size of the vocal cords and of the vocal tract.

The quality or color of a voice also depends on the singer's ability to develop and use various resonances by controlling the shape and size of the chambers through which the sound flows. It has been demonstrated electrographically in the form of "voice-prints" that, like fingerprints, no two voices are exactly alike.

In a technical sense, resonance is a relationship that exists between two bodies vibrating at the same frequency or a multiple thereof. In other words, the vibrations emanating from one body cause the other body to start vibrating in tune with it. A resonator may be defined as a secondary vibrator which is set into motion by the main vibrator and which adds its own characteristics to the generated sound waves.

There are two kinds of resonance: sympathetic resonance (or free resonance) and forced resonance (or conductive resonance) The essential difference between both types is what causes the resonator to start vibrating. In sympathetic resonance, there is no need of a direct physical contact between the two bodies. The resonator starts functioning because it receives vibrations through the air and responds to them sympathetically, as long as the resonator's natural frequencies of vibration coincide with the exciting oscillations. In forced resonance, the resonator starts vibrating because it is in physical contact with a vibrating body, which "forces" the resonator to replicate its oscillations.

Both types of resonance are at work in the human voice during speaking and singing. Much of the vibration felt by singers while singing is a result of forced resonance. The waves originated by the airflow modulated by the vibrating vocal folds travel along the bones, cartilages, and muscles of the neck, head, and upper chest, causing them to vibrate by forced resonance. There is little evidence that these vibrations, sensed by tactile nerves, make any significant contribution to the external sound.