1.  duet(n = noun.quantity) brace, couple, couplet, distich, duad, duo, dyad, pair, span, twain, twosome, yoke - two items of the same kind; Array
is a kind of 2, deuce, ii, two
has parts: fellow, mate
has particulars: doubleton

2.  duet(n = noun.group) duette, duo - two performers or singers who perform together; Array
is a kind of musical group, musical organisation, musical organization
has particulars: laurel and hardy

3.  duet(n = noun.group) couple, duo, twosome - a pair who associate with one another; "the engaged couple"; "an inseparable twosome"
is a kind of pair
has particulars: same-sex marriage

4.  duet(n = noun.communication) duette, duo - a musical composition for two performers; Array
is a kind of composition, musical composition, opus, piece, piece of music
has parts: primo, secondo

5.  duet(n = noun.act) pas de deux - (ballet) a dance for two people (usually a ballerina and a danseur noble); Array
is a kind of dance, dancing, saltation, terpsichore
is a part of ballet, concert dance
has parts: adagio

duet, n.
1 Mus. a a performance by two voices, instrumentalists, etc. b a composition for two performers.
2 a dialogue.

Derivative:
duettist n.

Etymology:
G Duett or It. duetto dimin. of duo duet f. L duo two

N  duality, dualism, duplicity, biplicity, biformity, polarity, two, deuce, couple, duet, brace, pair, cheeks, twins, Castor and Pollux, gemini, Siamese twins, fellows, yoke, conjugation, dispermy, doublets, dyad, span, two, twin, dual, dualistic, double, binary, binomial, twin, biparous, dyadic, conduplicate, duplex, biduous, binate, diphyletic, dispermic, unijugate, tete-a-tete, coupled, conjugate, both, both the one and the other.

N  music, concert, strain, tune, air, melody, aria, arietta, piece of music, work, number, opus, sonata, rondo, rondeau, pastorale, cavatina, roulade, fantasia, concerto, overture, symphony, variations, cadenza, cadence, fugue, canon, quodlibet, serenade, notturno, dithyramb, opera, operetta, oratorio, composition, movement, stave, passamezzo, toccata, Vorspiel, instrumental music, full score, minstrelsy, tweedledum and tweedledee, band, orchestra, concerted piece, potpourri, capriccio, vocal music, vocalism, chaunt, chant, psalm, psalmody, hymn, song, canticle, canzonet, cantata, bravura, lay, ballad, ditty, carol, pastoral, recitative, recitativo, solfeggio, Lydian measures, slow music, slow movement, adagio, minuet, siren strains, soft music, lullaby, dump, dirge, pibroch, martial music, march, dance music, waltz, solo, duet, duo, trio, quartet, quartett, septett, part song, descant, glee, madrigal, catch, round, chorus, chorale, antiphon, antiphony, accompaniment, second, bass, score, bourdon, drone, morceau, terzetto, composer, musician, musical, instrumental, vocal, choral, lyric, operatic, harmonious, Wagnerian, adagio, largo, larghetto, andante, andantino, alla capella, maestoso, moderato, allegro, allegretto, spiritoso, vivace, veloce, presto, prestissimo, con brio, capriccioso, scherzo, scherzando, legato, staccato, crescendo, diminuendo, rallentando, affettuoso, obbligato, pizzicato, desto, in notes by distance made more sweet, like the faint exquisite music of a dream, music arose with its voluptuous swell, music is the universal language of mankind, music's golden tongue, the speech of angels, will sing the savageness out of a bear, music hath charms to soothe the savage beast.