While critics have often dismissed the opera as a facile melodrama with confusions of plot—musicologist Joseph Kerman famously called it a "shabby little shocker"[1][2][3]—the power of its score and the inventiveness of its orchestration have been widely acknowledged.

The upper parts of the Castel Sant'Angelo, early the following morning A shepherd boy is heard offstage singing (in Romanesco dialect) "Io de' sospiri" ("I give you sighs") as church bells sound for matins.

Illica and Giuseppe Giacosa, the playwright who joined the project to polish the verses, needed not only to cut back the play drastically, but to make the characters' motivations and actions suitable for Italian opera.

In August, Puccini removed several numbers from the opera, according to his biographer, Mary Jane Phillips-Matz, "cut[ting] Tosca to the bone, leaving three strong characters trapped in an airless, violent, tightly wound melodrama that had little room for lyricism".

[32] For the Te Deum music, he investigated the melodies to which the hymn was set in Roman churches, and sought to reproduce the cardinal's procession authentically, even to the uniforms of the Swiss Guards.

[34] This apparently did not have its desired effect, as Illica wrote to Ricordi on the day after the premiere, "the great fuss and the large amount of money for the bells have constituted an additional folly, because it passes completely unnoticed".

[28] In act 2, when Tosca sings offstage the cantata that celebrates the supposed defeat of Napoleon, Puccini was tempted to follow the text of Sardou's play and use the music of Giovanni Paisiello, before finally writing his own imitation of Paisello's style.

[14] Puccini travelled to London for the British premiere at the Royal Opera House, Covent Garden, on 12 July, with Milka Ternina and Fernando De Lucia as the doomed lovers and Antonio Scotti as Scarpia.

[56] In Philipp Himmelmann's [de] production on the Lake Stage at the Bregenz Festival in 2007 the act 1 set, designed by Johannes Leiacker, was dominated by a huge Orwellian "Big Brother" eye.

[60] Gobbi, who in his later years often directed the opera, commented, "Unlike Floria, Cavaradossi knows that Scarpia never yields, though he pretends to believe in order to delay the pain for Tosca.

After the premiere, Ippolito Valetta of Nuova antologia wrote, "[Puccini] finds in his palette all colours, all shades; in his hands, the instrumental texture becomes completely supple, the gradations of sonority are innumerable, the blend unfailingly grateful to the ear.

"[47][61] However, one critic described act 2 as overly long and wordy; another echoed Illica and Giacosa in stating that the rush of action did not permit enough lyricism, to the great detriment of the music.

[62] The critics gave the work a generally kinder reception in London, where The Times called Puccini "a master in the art of poignant expression", and praised the "wonderful skill and sustained power" of the music.

[68] Music critic Charles Osborne ascribes Tosca's immense popularity with audiences to the taut effectiveness of its melodramatic plot, the opportunities given to its three leading characters to shine vocally and dramatically, and the presence of two great arias in "Vissi d'arte" and "E lucevan le stelle".

[70] By the end of the 19th century the classic form of opera structure, in which arias, duets and other set-piece vocal numbers are interspersed with passages of recitative or dialogue, had been largely abandoned, even in Italy.

In what critic Edward Greenfield calls the "Grand Tune" concept, Puccini retains a limited number of set-pieces, distinguished from their musical surroundings by their memorable melodies.

[78] After Tosca's "Non la sospiri" and the subsequent argument inspired by her jealousy, the sensuous character of the love duet "Qual'occhio" provides what opera writer Burton Fisher describes as "an almost erotic lyricism that has been called pornophony".

[33] The brief scene in which the sacristan returns with the choristers to celebrate Napoleon's supposed defeat provides almost the last carefree moments in the opera; after the entrance of Scarpia to his menacing theme, the mood becomes sombre, then steadily darker.

[79] In Scarpia's exchanges with Tosca the sound of tolling bells, interwoven with the orchestra, creates an almost religious atmosphere,[36] for which Puccini draws on music from his then unpublished Mass of 1880.

He joins with the chorus in the final statement "Te aeternum Patrem omnis terra veneratur" ("Everlasting Father, all the earth worships thee"), before the act ends with a thunderous restatement of the Scarpia motif.

[82] The act begins quietly, with Scarpia musing on the forthcoming downfall of Angelotti and Cavaradossi, while in the background a gavotte is played in a distant quarter of the Farnese Palace.

[36][84] As Cavaradossi is brought in for interrogation, Tosca's voice is heard with the offstage chorus singing a cantata, "[its] suave strains contrast[ing] dramatically with the increasing tension and ever-darkening colour of the stage action".

A lyrical andante based on Tosca's act 1 motif, this is perhaps the opera's best-known aria, yet was regarded by Puccini as a mistake;[87] he considered eliminating it since it held up the action.

[75] In the act's finale, Newman likens the orchestral turmoil which follows Tosca's stabbing of Scarpia to the sudden outburst after the slow movement of Beethoven's Ninth Symphony.

[93] Puccini insisted on the inclusion of these words, and later stated that admirers of the aria had treble cause to be grateful to him: for composing the music, for having the lyrics written, and "for declining expert advice to throw the result in the waste-paper basket".

[72] In the execution scene which follows, a theme emerges, the incessant repetition of which reminded Newman of the Transformation Music which separates the two parts of act 1 in Wagner's Parsifal.

Ten years later, in 1929, Sabajno returned to the opera for the third time, recording it, by the electrical process, with the orchestra and chorus of the Teatro alla Scala and with stars Carmen Melis and Apollo Granforte in the roles of Tosca and Scarpia.

[98][99] In 1938 HMV secured the services of the renowned tenor Beniamino Gigli, together with the soprano Maria Caniglia as Tosca and conductor Oliviero De Fabritiis, for a "practically complete" recording that extended over 14 double-sided shellac discs.

Erich Leinsdorf conducted the Rome Opera House orchestra and chorus with Zinka Milanov as Tosca, Jussi Björling as Cavaradossi and Leonard Warren as Scarpia.

More recent commended recordings have included Antonio Pappano's 2000 Royal Opera House version with Angela Gheorghiu, Roberto Alagna and Ruggero Raimondi.