Recitative in the 18th century is not the same as recitative in the 19th century, recitative written by French, Italian, and German composers are also not the same, and instrumental recitative and operatic recitative are also quite different.
It's a good question though.
The general traits, as established by Italian composers by the middle of the 17th century, of "recitative" are: the text was generally not repeated, the rate of harmonic change varied with the affect of the text, an overall slow harmonic rhythm unfolded over a generally static bass line (which gave the impression of declamatory freedom, though chord progressions were still clearly derived from the madrigal), the poetic accents were reinforced by harmonic change, and particularly affective passages or individual words were often supported with strong dissonance (another madrigal borrowing).
By the 18th century recitative came to be the principal vehicle for dialogue and dramatic action in opera, with the arias carrying the more lyric portions, although this traditional understanding of the separation of dramatic function is less rigorous than is sometimes supposed. Moments of intense dramatic crisis (disasters, irreconcilable decisions, general stress), mental confusion (particularly madness), magic scenes and other suitable moments were clothed with an enriched, colorful background, and were variously known as accompagnato (in France récitatif accompagné), stromentato, obbligato and the like. This perpetuated an infrequent usage of the 17th century, found in scores of Cavalli, Antonio Cesti, Lully, Steffani, Purcell and others, which gradually rose in prominence after 1700, with theater poets in the latter half of the 18th century often adding new verses to established texts to facilitate these musical diversions. Distinct from recitativo semplice by virtue of its rhythmic and melodic figuration in the accompanimental parts, rapidly shifting character and imitation of the passions of the text, over time it became customary to enlist the orchestras aid. In practice, the accompanimental orchestral voices generally sustained chords or played scales and short melodic figures (particularly after about 1740).
During the first decade of the 19th century the distinction remained intact between the conversational recitativo secco and the more declamatory recitativo accompagnato, both varieties being marked off from the set numbers by the use of versi sciolti (freely alternating lines of seven- and eleven-syllable verse). By 1820 this had become the rule for serious works, keyboard accompaniment being restricted to opera buffa and semiseria. In due course both types of recitative became subsumed into the scena. All passages intended to be delivered in the rhythm of ordinary speech continued to be marked recitativo, however, even for only a few bars, a practice that continued until the 1890s, as in Verdis Otello (1887) and Catalanis La Wally (1892). In the operas of Puccini and his successors, on the other hand, the term vanishes, being replaced by the marking a piacere in the voice-part and col canto in that of the orchestra.
As operas became more continuous during the course of the 19th century, recitative as such inevitably disappeared. Its legacy, however, can be found in the comparatively unvocalized delivery required in such operas as Debussys Pelléas et Mélisande (1902), Vaughan Williams Riders to the Sea (1937) and the Sprechgesang employed in the operas of Berg and Schoenberg. A modern variant of recitativo secco occurs accompanied by piano in Brittens The Rape of Lucretia (1946) and by harpsichord in Stravinskys The Rakes Progress (1951).
Recitative-like passages have often been used in instrumental music for special expressive or dramatic effect. Among the earliest examples are those in Kuhnaus Biblischer Historien (1700). Bonporti wrote a much-ornamented recitative for solo violin in no.5 of his Concerti a quattro op.11 (after 1727), but a more direct imitation is to be found in the works of later composers. Examples include the first of C.P.E. Bachs Prussian Sonatas (1742), Haydns Symphony no.7 (Le midi, 1761) and Sinfonia concertante hI:105 (1792), Mozarts Violin Concerto no.3 k216 (1775) and Beethovens piano sonatas op.31 no.2 (1802) and op.110 (18212). The passage for cellos and basses in the finale of Beethovens Choral Symphony is marked selon le caractère dun Récitatif, mais in tempo. Schoenbergs Variations on a Recitative for organ op.40 (1941) explores possibilities that other composers seem to have ignored.
(Source: Oxford Grove Dictionary of Music)
, set to music of rock-like simplicity, and in the Ninth Symphony, Schiller’s famous apostrophe to universal brotherhood. In the best early Romantic spirit, Beethoven was seeking a new basic level of human contact through basic song, as though without sophistication or artifice. 
