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cal theme or musical idea. A theme may be broken up into smaller sections, or it may have its notes grouped differently (rephrased), or its harmony changed, or its rhythm altered. Moreover, such changes may be made singly or in combination, resulting in an enormous variety of possibilities. Development is a basic procedure of composition, particularly in longer works. 2 The second section of a movement in SONATA FORM, in which the themes presented in the first section (called the EXPOSITION, def. 2) are reworked.

D-flat One of the musical tones (see PITCH NAMES), one half tone below D and one half tone above C. On the piano, D-flat is identical with C- sharp (see ENHARMONIC for an explanation). The

major scale beginning on D-flat is known as D-flat major. A composition based on this scale is said to be in the key of D-flat major, the KEY SIGNATUREfor

this key being five flats. For the location of D-flat on the piano, see KEYBOARD.

di For Italian musical terms beginning with di, such as di nuovo, see under the next word (NUOVO). diapason (English dı¯′′ ə pa¯′ zən; French dyApA ZÔN′). 1 A group of organ pipes that provide the basic tone of the instrument (see ORGAN;PRINCIPAL,

def. 1). 2 The entire range of a voice or instrument.

3 French for PITCH. 4 French for TUNING FORK.

diapason normal (dyApA ZÔN′′ nôr mAl′). The French term for CONCERT PITCH, which in 1859 was established as the A above middle C at a frequency of 435 cycles per second.

diatonic (dı¯′′ə ton′ik). 1 Pertaining to or contain-

ing the notes that make up an octave containing five whole tones and two half tones. Both the major and minor scales are diatonic, as are the CHURCH MODES.

For example, one such arrangement is F, G, A, B

b

, C, D, and E, constituting the scale of F major; the remaining notes, which do not belong to this scale, are termed chromatic. Naturally, the terms

“diatonic” and “chromatic” apply only when a specific key (scale) is in question. In music where no particular key is used (see ATONALITY) the terms

have no meaning. 2 Proceeding by scale degrees.

3 Using DIATONIC HARMONY.

diatonic chord A chord made up only of diatonic notes, for example, F–A–C in the key of F major; the chord F–A–C#, on the other hand, is called a chromatic chord, since it contains a chromatic note (C-sharp).

diatonic harmony Harmony that consists chiefly of diatonic chords (it is rarely possible to exclude all chromatic notes).

didgeridoo Also, didjeridu (did′jer i doo— ′′) Aus-

tralian aborigine. An end-blown straight natural trumpet, without a separate mouthpiece, that is used by Australian aborigines. The average instrument is 1 to 1.5 meters (39 to 59 inches) long, with a bore of 3.5 to 7.5 centimeters (1.3 to 2.9 inches) but excep- tionally large ones, 2.5 meters long, are used in spe- cial ceremonies. It sounds a bass drone with waves of high overtones. Among the aborigines the didgeridoo may be played only by men. In addition to ceremonial functions, it is used to accompany singing and dancing, supply rhythm and tone color as well as being used as a drone. Western composers use it occasionally, as Annea Lockwood does in

Thousand Year Dreaming (1993) for ten instruments

and Philip Glass in Voices (2001) for didgeridoo and organ.

Dies irae (de¯′a¯s e¯r′e) Latin: “day of wrath.” A section of the Roman Catholic Requiem Mass (the Mass for the dead) whose text and music date from the thirteenth century. Although early composers of Requiem Masses used the original monophonic (with a single voice-part) music for this section as aSEQUENCE, later composers, among them Mozart and Verdi, set the words to more dramatic music of their own. The original music has also been used to suggest the idea of death in some secular (non- religious) compositions, as by Saint-Saëns in his

Danse macabre (“Dance of Death”) and by

Berlioz in his Symphonie fantastique (“Fantastic Symphony”).

diferencia (de¯ fe ren′thà e¯ ä) Spanish: “variation.” A musical form consisting of THEME AND VARIA- TIONS. Many fine diferencias for lute and keyboard

instruments were written by Luis de Narvaez, Anto- nio de Cabezón, and other sixteenth-century Spanish composers. Narvaez was one of the first to use the form of theme and variations, which he developed to an extent extraordinary for his time.

differential tone See under TARTINI,GIUSEPPE. differential tone 107

digital piano An electric or electronic piano that produces sound through computer technology. The sound of such an instrument is generated by elec- tronic oscillators, originally by digital synthesis but more recently by sampled sound. With the flick of a switch it can produce the sound of either a grand piano or a harpsichord, or, in some models, the sound of any of 150 or more instruments. The earli- est electric keyboards, produced in the 1930s, had strings but no soundboard, with magnets picking up the strings’ vibrations. This version was replaced about 1960 by a piano that had tuned steel bars or reeds, struck by a hammer. Today’s digital piano has neither strings nor soundboard and can, with the aid of software and specialized CD players, allow the player to hear a piece in various ways, such as slow- ing down the tempo, isolating either the lefthand or righthand part, with the sound of a metronome, with orchestral accompaniment, record the player’s efforts, and so on. The size of a digital piano ranges from a three-octave portable keyboard to an 88-key full-size grand piano. See also PLAYER PIANO.

digital recording Also, laser recording. A means of recording sound that uses computer technology to translate musical or other sounds into a multitude of binary digits (hence “digital”), or bits, which are then reconverted into sounds by means of a laser and con- verter and can be amplified and played through loud- speakers. Earlier recording methods all are based on analog principles, that is, the grooves on a record are replicas (“analogs”) of the actual sound waves, and their fidelity (faithfulness to the original sounds) depends on how closely they correspond to it. To play back sounds the grooves are tracked with a needle or stylus, which further distorts the sound to some degree. Digital recording, developed in the late 1970s, uses neither groove nor stylus. Each sound, defined by its basic characteristics of pitch, loudness, timbre, and so on, is encoded as a binary number, and it is these numbers rather than the wave forms of the sounds that are recorded as a series of bits—strings of 1 and 0. The numerically defined sounds are immune to distortion. The bits are etched, in the form of tiny pits, into a

compact disk, or CD, which looks like a shiny alu-

minum disk with a clear plastic cover. To play the sounds back, a digital audio stylus, in which the

pickup is not a stylus but a small laser, is used. The laser shines a fine beam of light on the tiny pits and, by registering changes in reflected light, counts them. The count, interpreted by a special circuit called a digital- to-analog converter, spells out the musical wave form into its original shape, which can then be amplified and played through speakers. Compared to analog records, the digital technique produces more clarity of sound, greater depth and definition of the low bass (no longer constrained by the limited width of the record groove), total absence of scratch, hiss, and other back- ground noise, and no record wear. The compact disks are almost infinitely durable; since nothing but weight- less laser beams touches them during play, there is no abrasion. The coating of durable plastic prevents cor- rosion. However, because digital sound is so close to the original, it clearly shows up any errors on the part of record producers. Further, listeners accustomed to the extraneous noises of the concert hall and the dis- tortions of analog recording may at first find the very clarity and fidelity of digital sound quite strange. The original compact disk was designed mainly for classical music (its playing time of 70 minutes was based on the duration of Beethoven’s Symphony no. 9). Subsequently different digital formats were designed for popular music, a minidisk (MD) of 2.5 inches and a digital compact cassette (CDD). Still another format is the digital audio tape (DAT), a smaller than conventional cassette that can accom- modate more detail than compact disks and conse- quently is widely used by recording companies to make professional tapes. Still newer is the digital

video disc, or DVD, which combines digital video

production with digital sound. It is especially suit- able for recording opera, since typically a full-length opera can fit on a single disc.

Digital technology also has been extended to telecommunications techniques, enabling compact- disk sound to be transmitted over special telephone lines. First used for film soundtracks, this technol- ogy enables musicians to collaborate on a “live” recording even when they are physically separated by thousands of miles.

diluendo (de¯′′loo— en′dô) Italian. A direction to perform more and more softly, so the music seems to fade away.

dim. Also, dimin. An abbreviation for DIMINUENDO.

diminished chord A chord that contains one or more diminished intervals. The most important kinds of diminished chord are the diminished triad (for example, B–D–F) and the diminished seventh chord (a diminished triad plus a minor third, such as B–D– F–A

b

). See CHORDfor an explanation of these terms. diminished interval An interval that is one half tone smaller than the corresponding perfect or minor interval (see INTERVAL, def. 2, for an

explanation of these terms). In practice, the most

important diminished intervals are the diminished fifth (one half tone smaller than the perfect fifth) and diminished seventh (one half tone smaller than the minor seventh.)

diminuendo (de¯ me¯′′noo— en′dô) Italian. Another word for DECRESCENDO. Often abbreviated dim. or

dimin.

diminution Decreasing the time values of all the notes in a theme (short melody), so that, for exam- ple, all the quarter notes become eighth notes and the half notes become quarter notes. (The opposite process, in which, for example, all the quarter notes become half notes and the half notes become whole notes, is called AUGMENTATION.) Both diminution and augmentation are common means of varying a theme, and they are often used in fugues, as well as in sonatas and symphonies.

D’Indy, Vincent See INDY,D’,VINCENT.

dirge A song or instrumental piece expressing mourning; see LAMENT.

disc Another spelling for disk; see DIGITAL RECORDING.

discant (dis′kant). Another spelling of DESCANT.

discantus (dis kan′təs) Latin: “different song.”

1 Originally, a melody that was added to an already

existing melody. The main part was called CANTUS

and usually lay in the tenor, while the added part was generally above it, in the treble (soprano).

2 Music in which one or more such parts were

added, and, since such music in the twelfth century was in note-against-note style, the term also came to mean music in strict rhythm. 3 In the four- teenth century, when most polyphonic music was contrapuntal, the term was occasionally used as a synonym for COUNTERPOINT.

disco A style of dance music of the late 1970s and early 1980s, usually recorded. It is characterized by a relentless 4/4 beat, instrumental breaks, and erotic lyrics or rhythmic chants. An outgrowth of nonstop music played by disk jockeys who remixed records by boosting the bass and sequencing them into con- tinuous music, it was gradually superseded by FUNK. discord Another term for DISSONANCE.

disinvolto (de¯s′′e¯n vôl′tô) Italian. A direction to perform in a free, easy, spontaneous manner.

disjunct motion See under MOTION, def. 1. disk jockey Also, disc jockey, deejay, D.J. A per- son responsible for selecting, sequencing, and pre- senting recorded popular music in a discotheque or radio broadcast, as well as acting as master of cere- monies. Also see RAP;REGGAE.

Disklavier See under PLAYER PIANO.

dissonance (dis′ə nəns). Also, discord. A musi- cal interval or chord that sounds harsh or unpleasant (a chord or interval that sounds pleasant is called a

CONSONANCE). A dissonant interval or chord seems

restless and appears to call for RESOLUTION into a subsequent consonant interval or chord. From about 1500 to about 1900, all intervals except the unison, the major and minor third, the perfect fifth, the major and minor sixth, and the octave were classed as dissonances. Although these intervals and chords containing them could be employed, there were

dissonance 109

strict rules governing their use and the ways in which they had to be resolved into consonances. In most music after 1900, these rules are largely ignored, and the traditional distinction between con- sonance and dissonance is no longer made.

dissonant counterpoint See under CRAWFORD SEEGER,RUTH.

div. The abbreviation for DIVISI.

divertimento (de¯ ver′′te¯ men′tô) pl. divertimenti (de¯ ver′′te¯ men′te¯) Italian. In the late eighteenth century, a composition in several movements (usu- ally more than four) scored for a small instrumental group and intended chiefly to be entertaining (occa- sionally even humorous). The best-known com- posers of divertimenti are Haydn and Mozart, each of whom wrote numerous works of this kind. Closely related to the divertimento in form are the

SERENADEand CASSATION.

divertissement (de¯ ver te¯s mäN′). 1 The French term for DIVERTIMENTO. 2 A composition based on

familiar tunes. 3 A ballet, dance, or instrumental piece inserted between the acts or elsewhere in a French opera of the baroque period (1600–1750), having no connection with the plot but serving purely to entertain.

Divine Office See OFFICE.

divisi (de¯ ve¯′se¯) Italian: “divided.” A term used in scores to indicate that a group of instruments that normally play one part are to play two or more sepa- rate parts, often written on the same staff. The direc- tion is most often given to a string section, such as the first violins. The end of the divisi section, when the instruments are to resume playing one part together, is usually marked TUTTIor UNISONO. Often

abbreviated div.

In document UNIVERSITAT POLITÈCNICA DE VALÈNCIA ANÁLISIS DE LA INFLUENCIA DE LAS CORRIENTES DE MACROCELDA EN LA CORROSIÓN DE LOSAS DE HORMIGÓN ARMADO (página 37-41)