Though librettos of Metastasio went on being set and staged into the 1820s and occasionally beyond, by the 1760s more progressive spirits in writing and staging were entering a new age of sensibility, enlightenment, ‘sublime simplicity’ and growing concern for theatrical realism, the last partly expressed in a canonization of Shakespeare and a fresh respect for the arts of comedy. One aspect of this was the appeal that buffo acting came to have for serious opera lovers. The tiny, often two-person troupes performing farcical intermezzos between the acts of opera seria and the rather larger companies giving more extended opere buffe had developed a style of acting that was brisker, saltier and more immediately alluring, if not a great deal less governed by convention, than that seen in loftier opera. The unpretentiousness of this style and the leeway it gave for sharp observation of contemporary life endeared it to such observers as Arteaga and de Brosses, who saw its vivacity and ‘air of truth’ as rebukes to the traditional high operatic stage's tendency to what had come to seem stiffness and frigidity. At a time when David Garrick (the living demonstration that ‘Shakespeare and Nature were the same’) was shifting the norm of serious acting in spoken theatre away from weighty, slow-moving declamation towards a more energetic, pantomimic mode, it is likely that some of the more seemly aspects of buffo style, along with some Garrickian traits, were sharpening the immediacy of serious operatic acting and increasing its air of truth.
Garrick was the model for several of the new men of operatic Europe in the mid-18th century, not least Noverre, for whom he was ‘the Proteus of our time’ and an inspiration behind Noverre's campaign to unmask the dancers in opera and so increase their histrionic potential. But if Garrick was a Proteus, it was the Gluck of the ‘reform’ operas who was seen by his admirers as the modern Prometheus where, inter alia, staging was concerned. One of them in the 1770s describes him as having to deal at first with principal singers whose acting was either lifeless or grotesquely mannered and with ‘a collection of mannequins called a chorus’; but ‘Prometheus shook his torch and the statues came to life’, the principals realizing that the idiom of Gluck's music needed only to be felt to bring strong and true stage impersonation with it, while the chorus members in his operas were ‘amazed to discover that they were actors’.
Garrick and Gluck, of course, were not alone responsible for all theatrical change at the time; but praise of this kind provides a frame for such things as the poet Verazi's stagings of his own librettos in the 1760s and 70s, noted for their treating the chorus ‘as actors, not statues’; his printing his librettos with stage directions for elaborate business during the normally direction-free da capo arias; the increasing trouble taken by such composers as Jommelli to construct buffo ensembles which would permit ‘natural’ acting throughout; the growing tendency of the operatic stage space to be characterized by chiaroscuro in lighting, local colour in décor and asymmetry in the deployment of supernumeraries, dancers and scenery; the praises heaped on a singer like Sophie Arnould for her tenderness, energy, soul, sentiment and sensibility; and the determination of Gaetano Guadagni, who had learnt directly from Garrick and created the leading role in Orfeo ed Euridice (1762), to identify with his roles so fully that he refused to acknowledge applause after an aria or give encores.
Few singers may have gone as far as Guadagni in this; but his ideal chimes with a concept of opera involving a carefully monitored synthesis of theatrical arts, all blending together to present a heightened virtual actuality which will enthral, elevate and edify. The concept attracted support in the later 18th century, although there were differing views as to who should finally be responsible for the careful monitoring. Noverre and Algarotti, influentially urging this conscious integration of the arts as opposed to the traditional laissez-faire, both insisted that it was the poet-librettist who, as the begetter of the opera, should be the guardian of its wholeness, and that it was for the other theatre artists to embody the poet's unifying conception. Noverre further emphasized the need for the executive quintet of composer, designer, machinist, ballet-master and costumier to work closely together and for the poet to be on call throughout, which is what happened in the case of the team working on Orfeo. It was certainly an authority structure assured of some success in court theatres where the local prince himself was the librettist (or at least the influential drafter of scenarios). Elsewhere it might be the court composer, as with Jommelli at Stuttgart in the 1750s and 60s under the watchful eye of Duke Carl Eugen. According to Christian Schubart, Jommelli used his knowledge of singers, instrumentalists, audiences and theatre acoustics, plus the close cooperation of designers, machinists and choreographers, ‘to move and uplift the coldest listener's heart and soul with one great totality’. Or it might be the court intendant for music and drama, as seems to have been the case with Count von Seeau at Munich in 1780–81 when Mozart and Varesco's Idomeneo was being prepared and rehearsed. Mozart's letters home suggest a careful collaboration under Seeau's control between composer, conductor, scenographer and choreographer. The lack of the librettist on the spot to advise singers about stage action suggests that the principals were expected to be largely self-reliant and to use appropriate modifications of well-tried seria and Gluckian techniques, taking advice where they found it. They would almost certainly have found it from Mozart in his role as composer-répétiteur, with his earnest concern that recitative should be fast-moving, spirited and fiery in performance, that singers should act, and that the best criterion for librettists, composers and performers alike was theatrical effectiveness.