allegro [I]—fast, lively tempo. From the Italian word for cheerful or gay.
andante [I]—moderately slow tempo (e.g. walking). Faster than adagio but slower than allegretto
chamber music, Kammermusik [G], musique de chambre [F], musica da camera [I], musica cameralis [L]—"Classical Music" for a small ensemble, generally 8 or fewer players with a canonical emphasis on 3-6 players. explore
Flute quartet—Common name for popular chamber ensemble (work) comprising flute, violin, viola and cello (rather than 4 flutes!). This ensemble was especially popular in the "gallant" early classical period particularly for domestic music making by royal and common flutist alike.
oboe quartet—ensemble/work for oboe and strings, typically the traditional string trio comprising violin, viola, and cello. Note, "oboe quartet" might also refer to a quartet of oboes, but the frequency of this quartet for oboe and strings warrants the traditional name. Explore the oboe quartet | wiki
opus [L], opera[pl], Op., Opp, WoO, Op. posth—work, as in a work of art. For unique identification, publishers/composers often assign an "opus number", abbreviated as "Op." (e.g. Op. 1). A range of works by opus number, uses the plural "opp." (e.g. "Opp. 1-3"). A single opus number may refer to a collection of works (e.g. a set of quartets) giving rise to designations like "Op. 1, No. 4". For misc. works without opus numbers, "WoO" is often used (e.g."Without Opus"). Posthumously assigned numbers may use "Op. posth". Opus numbers may not precisely reflect chronology (publication vs. composition), can be erroneous, sparse or duplicative. Thus, the works of some historically important composers may use separate catalog numbers (e.g. Bach, Haydn, Schubert). See wiki
quartet, quatuor [F], quartett [G], quartetto [I], cuarteto [S]—ensemble or work for four players the most important examples being the string quartet and the piano quartet
string trio, Streichtrio [G], Trio d'archi [I], Trio à cordes [F], Trío de cuerdas [S]
—a work for three stringed instruments, most commonly violin, viola, and cello. A more rarefied form than the string quartet, perhaps because the texture is sparse (each instrument highly exposed) and the means are more difficult for natural harmonic richness. But these become challenges and assets in the great trios. Trios almost always emphasize countrapuntal writing with each of the three players in strong relief. Explore the string trio | wiki