Alto (L. altus: “high”). The voice type between mezzo soprano and tenor whether sung by a male or female.
Aria (It.: “air”). A solo from an opera or oratorio.
Arpeggio (It.: n. der. of arpeggiare, orig. “to play the harp”). 1. The sounding of the notes of a chord in succession instead of simultaneously. 2. A chord thus sounded.
Arytenoid (Gk.: arytainoedes: “ladle-shaped”). Pertaining to either of two small cartilages at the back of the larynx.
Baritone (Gk. barýtonos: “deep-sounding”). A male voice between tenor and bass.
Bass (L. bassus: “low”). The lowest adult male voice.
Bel canto (It.: “beautiful singing”). The term was not in common usage until around 1880, when it may have been used in reaction to the Wagnerian vocal style. In present usage it usually refers to the Italian singing methods of the 17th and 18th centuries with its emphasis on virtuosity and beauty of tone.
Belt –n. 1. [A style or technique of singing] in which the larynx is slightly higher than in the classical voice, and the vocal cords are held tightly together for a longer period of time. . . . The shape of the word and how it is spoken is intrinsic to the sound. The sound seems [extremely] forward [in “placement”] . . . but is not nasal. . . . The space inside the mouth is not as large as in the classical technique. . . . [True] belt is not chest voice nor an extension of chest voice into the higher register. [Sullivan (1985), 16.] –v.t. 1. As used commonly, to sing (a song) loudly and energetically.
Break. A muscle spasm causing an interruption in the normal production of sound. [Schmidt (1994), 282.]
Castrato (It.: Ger. Kastrat). A eunuch, or one who has been castrated. In music, a male singer who has been castrated before puberty in order to preserve the soprano or contralto range of his voice. [The New Grove.]
Coloratura (It.: “coloring”). 1. Runs, trills, and other florid decorations in vocal music. 2. A high soprano who specializes in such music.
Countertenor. A male alto, normally a falsettist.
Cricoid (Gk.: krikoides, “ring-shaped”). Pertaining to a ring-shaped cartilage at the lower part of the larynx.
Croon (Du.: cronen, to lament ). To sing or hum in a soft, soothing voice. Examples: Perry Como, Bing Crosby, etc.
Da capo (It.: “from the head”). Return to the beginning.
Diaphragm (Gk.: dia, “through” + phrágma, “fence”). Wall of muscle and connective tissue separating the thoracic cavity from the abdominal cavity.
Epiglottis (Gk.: epi, “on, over” + glottis, “tongue”). A flap of cartilage behind the tongue that helps close the opening to the trachea during swallowing.
Fach. A voice type. In Germany, Austria, and Switzerland a system which categorizes singers in order to aid the singer in the preparation of roles that are well suited for them and their career. It can also enable the opera house manager to plan future seasons, as well as cast roles. [See also Handbuch der Oper by Rudolf Kloiber.]
Falsetto (It.: Fr. fausett; Ger. Falsett, Fistelstimme). The treble range produced by most adult male singers through a slightly artificial technique. . . . . When falsetto is brought into use . . . a permanent oval orifice is left between the edges [of the vocal cords] through which a certain volume of air escapes. Either a short length or the whole of the membranous vocal cords may be separated; the size of the aperture varies and is found to increase as the pressure of air expelled from the lungs is raised. . . . In falsetto the extreme membranous edges of the vocal cords appear to be the only parts in vibration; the mass corresponding to the inner part of the thyro-arytenoid muscle remains motionless. [The New Grove.]
Fioritura (It.: “flowery”).
Formant. One of the regions of concentrated energy, prominent on a sound spectrogram, that collectively constitute the frequency spectrum of a speech [or singing] sound. (See also Singer’s formant.)
Helden- (G.: prefix, der. of Held, “hero”). A type of powerful dramatic voice used particularly in the operas of Richard Wagner, e.g., Heldentenor, Heldenbaritone.
High C. For women, the note c5; for men, the note c4.
Hosenrolle (G.: “trouser or pants role”). A man’s part sung by a woman. Examples: Octavian in Strauss’ Der Rosenkavalier, Cherubino in Mozart’s Le Nozze di Figaro.
Hyoid bone. A U-shaped bony or cartilaginous structure at the base of the tongue.
International Phonetic Alphabet (IPA). A set of symbols and modifying signs defined by the International Phonetic Association to provide a consistent and universally understood system for transcribing the speech sounds of any language.
Larynx. Scientific term for the voice box. A muscular and cartilaginous structure at the upper end of the vertebrate trachea, in which the vocal cords are located.
Messa di voce. A vocal exercise in which the singer initiates a note pianissimo, crescendos gradually to fortissimo, and then gradually diminuendos to pianissimo.
Mezza voce (It.: “half voice”).
Mezzo Soprano. (It.: “middle soprano”). A female voice or voice part intermediate in compass between soprano and contralto.
Musico. During the 17th and 18th centuries, another term for a castrato.
Opera (L.: orig. pl. of opus, “work”). A dramatic work in which the roles are entirely or partially sung.
Oratorio (der. from the musical services in the church of the Oratory of St. Philip Neri in Rome). An extended musical work based on a religious theme, for solo voices, chorus, and orchestra, and performed without action, costume, or scenery.
Passagio (It.: “passage”).
Pharynx. (Gk.: phárynx, “throat”). The portion of the alimentary canal, with its membranes and muscles, that connects the mouth and nasal passages with the larynx.
Recitative (L.: recitare, “to read aloud”). A style of vocal music intermediate between speaking and singing.
Resonance (L.: resonantia, “echo”) 1. Amplification of a source of speech sounds, especially of phonation, by sympathetic vibration of the air, especially in the cavities of the mouth, nose and pharynx. 2. A characteristic quality of a particular voiced speech sound imparted by the distribution of amplitudes among the cavities of the head, chest and throat.
Singspiel. (G.: “Sing-play”). A literal translation of the Italian dramma per musica. Used in the 17th and early 18th centuries to refer both to works sung in their entirety and to those having some spoken dialogue. In the second half of the 18th century its meaning was restricted to the latter type [Grout (1965), 113.]
Song. A short lyric or narrative text set to music. [From “Song,” Microsoft® Encarta® Online Encyclopedia 2002.]
Soprano (L. supra “above” + ano adj. suffix). The highest singing voice in females and boys.
Sotto voce (It.: “under [the] voice”). In a very soft voice, so as not to be overheard.
Soubrette (Fr.: “lady’s maid”). A maidservant in a play or opera, especially one displaying coquetry, pertness, and a tendency to engage in intrigue.
Sprechgesang (G.: “speak-song”). A vocal style intermediate between speech and singing but without exact pitch intonation.
Sprechstimme (G.: “speak-voice”). Synonymous with Sprechgesang.
Tenor (L. tenere: “to hold”). In polyphony between about 1200 and 1500, the structurally fundamental voice or instrument; by the 15th century it came to signify the male voice that sang such parts, and later it was applied not only to singers covering roughly c2 to a4 but also instrumental parts occupying approximately that register. [The New Grove.]
Tenor altino. A highly specialized type of tenor voice that extends into the treble region in true head tone without breaking into falsetto.
Thyroarytenoids. Scientific term for the vocal cords, named for the cartilages to which they attach.
Thyroid cartilage. Scientific term for the Adam’s apple.
Timbre. The characteristic quality of a sound, independent of pitch and loudness, depending on the number and relative strengths of its component frequencies, as determined by resonance.
Trachea. Scientific term for the windpipe. A tube that extends from the larynx to the bronchi, serving as the principle passageway of air to and from the lungs.
Trill. A rapid alternation of two adjacent musical tones.
Vocalises. Vocal exercises.
Voix mixte (Fr.: “mixed voice”). A blending of the chest and head registers.
Yodel. A style of singing with frequent changes between chest register and falsetto.

Unless otherwise indicated definitions are from the 16th edition of the Random House New World Collegiate Dictionary.