Singing “in parts” means that each voice (such as soprano, tenor, alto, and bass) has its own independent line to follow. The contents of that line will be written out, and will depend on the composer or arranger and the harmonic structure of the piece. These parts may form consonances or dissonances with one another, and they may move in parallel motion (going in the same direction), contrary motion (going in opposite directions) or oblique motion (one stays on a note while the other is moving).
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Singing “in unison” means that all the voices are singing the “same” line. I put “same” in quotes because, as you note in your last paragraph, they may be in different octaves. With voices, this almost always means the men are singing the line one octave below the women.
A choir (also known as a chorale or chorus) is a musical ensemble of singers. Choral music, in turn, is the music written specifically for such an ensemble to perform. Choirs may perform music from the classical music repertoire, which spans from the Medieval era to the present, and/or popular music repertoire. Most choirs are led by a conductor, who leads the performances with arm and face gestures.
A body of singers who perform together as a group is called a choir or chorus. The former term is very often applied to groups affiliated with a church (whether or not they actually occupy the choir) and the second to groups that perform in theatres or concert halls, but this distinction is far from rigid. Choirs may sing without instrumental accompaniment, with the accompaniment of a piano or pipe organ, with a small ensemble (e.g., harpsichord, cello and double bass for a Baroque era piece), or with a full orchestra of 70 to 100 musicians.
The term “Choir” has the secondary definition of a subset of an ensemble; thus one speaks of the “woodwind choir” of an orchestra, or different “choirs” of voices and/or instruments in a polychoral composition. In typical 18th- to 21st-century oratorios and masses, chorus or choir is usually understood to imply more than one singer per part, in contrast to the quartet of soloists also featured in these works.
Classical and Romantic music
Composers of the late 18th century became fascinated with the new possibilities of the symphony and other instrumental music, and generally neglected choral music. Mozart’s choral works, though not as numerous as his works for other media, stand out as some of his greatest (such as the “Great” Mass in C minor and Requiem in D minor, the latter of which is often considered the greatest Requiem Mass of all time). Haydn became more interested in choral music near the end of his life following his visits to England in the 1790s, when he heard various Handel oratorios performed by large forces; he wrote a series of masses beginning in 1797 and his two great oratorios The Creation and The Seasons. Beethoven wrote only two masses, both intended for liturgical use, although his Missa solemnis is probably suitable only for the grandest ceremonies due to its length, difficulty and large-scale scoring. He also pioneered the use of chorus as part of symphonic texture with his Ninth Symphony and Choral Fantasia.
In the 19th century, sacred music escaped from the church and leaped onto the concert stage, with large sacred works unsuitable for church use, such as Berlioz’s Te Deum and Requiem, and Brahms’s Ein deutsches Requiem.Rossini’s Stabat mater, Schubert’s masses, and Verdi’s Requiem also exploited the grandeur offered by instrumental accompaniment.
Oratorios also continued to be written, clearly influenced by Handel’s models. Berlioz’s L’enfance du Christ andMendelssohn’s Elijah and St Paul are in the category. Schubert, Mendelssohn, and Brahms also wrote secular cantatas, the best known of which are Brahms’s Schicksalslied and Nänie.
A few composers developed a cappella music, especially Bruckner, whose masses and motets startlingly juxtapose Renaissance counterpoint with chromatic harmony. Mendelssohn and Brahms also wrote significant a cappella motets.
The amateur chorus (beginning chiefly as a social outlet) began to receive serious consideration as a compositional venue for the part-songs of Schubert, Schumann, Mendelssohn, Brahms, and others. These ‘singing clubs’ were often for women or men separately, and the music was typically in four-part (hence the name “part-song”) and either a cappella or with simple instrumentation. At the same time, the Cecilian movement attempted a restoration of the pure Renaissance style in Catholic churches.
The early modernist composers, such as Richard Strauss, Sergei Rachmaninoff and Max Reger contributed to the genre. Ralph Vaughan Williams’s Mass in G minor harks back to the Renaissance style while exhibiting the vibrancy of new harmonic languages. Vaughan Williams also arranged English and Scottish folk songs. Arnold Schoenberg’sFriede auf Erden is a tonal kaleidoscope, whose tonal centers are constantly shifting (his harmonically innovative Verklärte Nacht for strings dates from the same period). Ukrainian composer Mykola Leontovych also explored new ways of harmonizing and arranging Ukrainian folk songs, producing masterpieces such as Dudaryk and Shchedryk, the latter of which featured a four-note ostinato theme and became a popular Christmas carol known as Carol of the Bells after it was translated by Peter J. Wilhousky.
The advent of atonality and other non-traditional harmonic systems and techniques in the 20th century also affected choral music. Serial music is represented by choral works by Arnold Schoenberg, including the anthem Dreimal Tausend Jahre, while the composer’s signature use of sprechstimme is evident in his setting of Psalm 130 De Profundis. Paul Hindemith’s distinctive modal language is represented by both his a cappella Mass and his Six Chansons (to texts by Rilke), while a more contrapuntally dissonant style comes through in his secular requiem,When Lilacs Last in the Dooryard Bloom’d. Olivier Messiaen also demonstrates dissonant counterpoint in his Cinq Rechants, which tell the Tristan and Isolde story. Charles Ives’ psalm settings exemplify the composer’s incomparably radical harmonic language. Tone clusters and aleatory elements play a prominent role in the choral music of Krzysztof Penderecki, who wrote the St. Luke Passio, and György Ligeti, who wrote both a Requiem and a separate Lux Aeterna. Milton Babbitt incorporated integral serialism into works for children’s chorus, while Daniel Pinkham wrote for choir and electronic tape. Meredith Monk’s Panda Chant and Astronaut Anthem explore overtones in an unconventional text setting. Though difficult and rarely performed by amateurs, pieces that demonstrate such unfamiliar idioms have found their way into the repertories of the finest semi-professional and professional choirs around the world.
More accessible styles of choral music include that by Benjamin Britten, including his War Requiem, Five Flower Songs, and Rejoice in the Lamb. Francis Poulenc’s Motets pour le temps de noël, Gloria, and Mass in G are often performed. A primitivist approach is exemplified by Carl Orff’s widely performed Carmina Burana. In the United States, Aaron Copland, Samuel Barber, and Randall Thompson wrote signature American pieces. In Eastern Europe, Béla Bartók and Zoltán Kodály wrote a small amount of music for choirs. Frank Martin’s Mass for double choir combines modality and allusion to Medieval and Renaissance forms with a distinctly modern harmonic language and has become the composer’s most performed work.
a cadence (Latin cadentia, “a falling”) is “a melodic or harmonic configuration that creates a sense of resolution [finality or pause].” A harmonic cadence is a progression of (at least) two chords that concludes a phrase, section, or piece of music. A rhythmic cadence is a characteristic rhythmic pattern that indicates the end of a phrase.
A cadence is labeled more or less “weak” or “strong” depending on its sense of finality. While cadences are usually classified by specific chord or melodic progressions, the use of such progressions does not necessarily constitute a cadence—there must be a sense of closure, as at the end of a phrase. Harmonic rhythm plays an important part in determining where a cadence occurs.
Classification of cadences in common practice
Cadences are strong indicators of the tonic or central pitch of a passage or piece. Edward Lowinsky proposed that the cadence was the “cradle of tonality.”
In music of the common practice period, cadences are divided into four types according to their harmonic progression: authentic, plagal, half, and deceptive. Typically, phrases end on authentic or half cadences, and the terms plagal and deceptive refer to motion that avoids or follows a phrase-ending cadence. Each cadence can be described using the Roman numeral system of naming chords:
Authentic (also closed, standard or perfect) cadence: V to I (or V–I). A seventh above the root is often added to create V. The The Harvard Concise Dictionary of Music and Musicians says, “This cadence is a microcosm of the tonal system, and is the most direct means of establishing a pitch as tonic. It is virtually obligatory as the final structural cadence of a tonal work.” The phrase perfect cadence is sometimes used as a synonym for authentic cadence, but can also have a more precise meaning depending on the chord voicing:
Perfect authentic cadence: The chords are in root position; that is, the roots of both chords are in the bass, and the tonic (the same pitch as root of the final chord) is in the highest voice of the final chord. A perfect cadence is a progression from V to I in major keys, and V to i in minor keys. This is generally the strongest type of cadence and often found at structurally defining moments.
This strong cadence achieves complete harmonic and melodic closure.” It has to be noted that Beethoven in particular gets so much mileage out of this cadence as for it to become one of his most characteristic and recognizable musical thumbprints. The Diabelli Variations and the C major climax of the slow movement of the Opus 132 String Quartet – even though it is described as being in Lydian mode on F – are two powerful examples.