Obbligato (Italian: obligatory) is often used
as a noun in English, in spite of its derivation. It is used to
an additional instrumental part that cannot be omitted, particularly
a solo instrument adds an accompanying melody in some baroque vocal
There is, for example, a well known violin obbligato to the
aria Laudamus te, in the B minor Mass of Bach.
The oboe is a double-reed instrument, an
part of the woodwind section of the modern orchestra. The mechanism of
its keys underwent considerable development in the 19th century. In
times it formed an important part of the outdoor military band, but the
Western symphony orchestra normally uses a pair of instruments. The
d’amore is the alto of the oboe family, used in the baroque period, and
the tenor is found in the cor anglais or, in the mid-18th century, in
oboe da caccia. The tone of the instrument, much affected by different
methods of cutting the reeds, can impart a characteristic sound to a
A scale formed by alternating wholetones and
according to the design: wholetone - semitone - wholetone -
- wholetone - semitone - wholetone - semitone. The upper tone of
each semitone has a tonic relation with the adjacent pitch below
(ex: C Db Eb E F# G A Bb)
The octave is an interval of an eighth, as
from the note C to C or D to D. The first note can have a sharp or flat
providing the last note has the corresponding sharp or flat (i. e. C
to C sharp).
The feature of musical perception according
all pitches separated by one or more perfect octaves are regarded as
to the same "pitch class" or as being in some sense equivalent.
is reflected in the system of Western pitch names, in which the seven
employed are repeated for each octave.
An octet is a composition for eight
The ondes Martenot, an electronic instrument
by the French musician Maurice Martenot, produces single sounds by
of a keyboard that controls the frequencies from an oscillator. It has
a wide range and offers the possibility of glissando. It became popular
among French composers, including Milhaud, Honegger, Koechlin, Schmitt,
Ibert, Jolivet, Messiaen and Boulez. Varèse also wrote for it,
he did for the less versatile electronic instrument, the theremin.
An opera is a drama in which most of the
all or most of their parts. The form developed at the end of the 16th
in Italy, from where it spread to other regions of Europe, although it
never became a regular part of London musical life until the early 18th
century. Internationally Italian opera has proved immensely important
popular, while opera in France underwent independent development in the
later 17th century under the Italian-born composer Lully. The 19th
brought particular developments in German romantic opera and in the
music-dramas of Wagner. The word opera covers a wide variety of
forms, from the Orfeo of Monteverdi to The Threepenny Opera
of Kurt Weill and Berthold Brecht of 1928, derived from the English
Beggar’s Opera two centuries earlier.
Opéra bouffe is the French term for
operetta of composers such as Offenbach in 19th century France.
Opera buffa is Italian comic opera,
in the form it took in early 18th century Italy.
French opéra comique originally purely
and later more sentimental in mood, included spoken dialogue,
Opera seria was the form of Italian serious
that held sway from the reforms of the early 18th century for a hundred
years. It came to be governed by strict rules as to subject and
and underwent reform in the interests of greater realism in the second
half of the 18th century with the composer Gluck.
Operetta is light opera, a development
the 19th century, exemplified in the work of Offenbach in France and
Strauss the younger in Vienna.
Opus (= Latin: work) is generally used in the
of a composer’s works by opus numbers, usually abbreviated to Op. Since
the Latin plural opera would lead to unnecessary confusion it is best
although the alternative opuses remains an unsatisfactory substitute.
numbers are not always a guide to the date of composition or even to
date of publication.
Oratorio has its origin in the musical
used by the followers of St. Philip Neri, the Oratorians, a religious
founded in 1575, although it has a possible remoter origin in the
drama of the Middle Ages. Forms of oratorio change, but it remains
a work in which religious texts often with a narrative content are set
for performance by singers and instruments. The oratorio underwent
developments throughout Europe, with the 17th century composer
and his successors in Italy, Charpentier in France, and later with
and others in Germany and, above all, Handel in the English oratorio of
the early 18th century.
The orchestra, the dancing-place of the
theatre, came, in the early 18th century, to have its modern meaning as
a group of instrumental performers of varied number, although this
still met with objections at the time. The size and composition of the
orchestra has differed from century to century, but during the course
the 17th century the string section developed as a five-part and later
as a four-part section, with first and second violins, violas and
and double basses, the last two playing the same part, although the
basses would sound an octave lower. In the later 18th century it became
usual to have in the orchestra an additional pair of French horns and a
pair of oboes, doubling flute as necessary, with a bassoon doubling the
bass. By the end of the 18th century a larger ensemble that included
necessary a pair of trumpets and drums was usual. In the 19th century
already used by Mozart and Haydn, became a regular part of the woodwind
section, in addition to flutes, oboes and bassoons. The brass section
to include trombones, instruments earlier used for special purposes
as well as trumpets, to be extended to instruments of lower range
the century. The 20th century has brought an extension of the
section. The number of players involved in a full symphony orchestra
grown very considerably, with over sixty string players, and a possible
forty or more wind and percussion players. This compares with Mozart’s
Salzburg orchestra of 23 string players and a dozen or so wind-players
and the orchestras of less prosperous princedoms, which might employ
smaller forces, a dozen or less string players and four or five wind
Orchestration is the art of arranging music
orchestra or the way in which this is done.
ordered sets are those in which the sequential ordering of elements
not change. The only allowable transformations are TTOs.
The organ is a keyboard instrument in which
is produced by air passing through pipes of various size and
to give a wide variety of pitches and timbres. The instrument has its
Western origin in the Hellenistic period, with the water-organ of
Varying in size and mechanical efficiency, the organ had by the later
century given rise to an important school of performance, leading
to the achievement of Johann Sebastian Bach in the first half of the
century. Technical developments have taken place since then, giving
greater versatility to the king of instruments.
Medieval polyphonic setting of plainsong.
Ostinato (Italian: obstinate) indicates a
repeats the same rhythm or melodic element. The basso ostinato or
bass occurs in the ground bass of baroque arias where a melody is set
a repeated bass pattern. Ostinato is used by the Bavarian composer Carl
Orff in his instrumental teaching methods, where it may form a basis
improvisation by pupils.
The overture (= French: ouverture; German:
Italian: sinfonia) is an introductory piece, often designed to initiate
an opera or other dramatic work. The late 17th century French overture
of Lully opens with a slow section in dotted (uneven) rhythm, followed
by a fugal section, before the return of the slow opening. The Italian
overture provides the origin of the symphony, with two fast movements
a central slow movement. The word Ouvertüre or Ouverture is
used to mean an orchestral suite, as in the four orchestral suites of
Sebastian Bach. In the 19th century the overture became also a possible
independent composition, a concert movement, often with literary or
associations, or an occasional connotation. Early examples of these
in Mendelssohn’s Overture A Midsummer Night’s Dream, originally
as a concert overture, or in the programmatic overtures of Berlioz.