Zelmira was composed with an eye to eh proposed Viennese tour of impresario Barbaja's Neapolitan company and opened that season on 13 April 1822. The major roles were written for Naples's fine company: Isabella Colbran (who, between the Neapolitan and Viennese premieres, became the composer's wife), Andrea Nozzari (Antenore), with his unusual extension at the top and bottom registers and a heroic vocal quality, and Giovanni David (Ilo), with a stratospheric range and unsurpassed ability in florid music.
Zelmira, daughter of Polidoro, elderly king of Lesbos, is married to Ilo, a prince of Troy. In Ilo's absence, Lesbos was conquered by Azorre, ruler of Mitilene. Zelmira has hidden Polidoro in the royal mausoleum; pretending to side with Azorre, she announced that her father was in the temple, which Azorre then burned. Antenore, aspiring to rule Mitilene, has secretly had Leucippo assassinate Azorre, accusing Zelmira of the deed. Ilo returns; when Zelmira greets him, they are surrounded by others, so that she has to conceal what has happened. Antenore and Leucippo, plotting to kill Ilo and his son, persuade Ilo that Zelmira has murdered Polidoro and now plans to kill him. The high priest crowns Antenore king. Ilo searches desperately for his son, whom Zelmira has consigned to the care of her friend Emma. Ilo collapses with grief, and Leucippo tries to stab him. Zelmira disarms Leucippo, who promptly accuses her of trying to kill her husband. She is arrested.
Leucippo and Antenore suspect that Polidoro is not dead and free Zelmira in order to discover her father's whereabouts. Polidoro tells Ilo of Zelmira's self-sacrifice, and Ilo takes up arms against Antenore. Leucippo tricks Zelmira into revealing her father's refuge, and Polidoro is captured. In the prison, Antenore and Leucippo are about to kill Polidoro when Ilo and his troops arrive and Antenore and Leucippo are carried off in chains. To general rejoicing Zelmira restores Polidoro to the throne.
In Zelmira the experimentation of the preceding years re¬aches a culmination. Forgoing an overture, the opera begins directly with the introduction, establishing a dark, dramatic tone that dominates much of the work. The harmonic language features intense chromaticism, and the minor mode is much in evidence. Antenore's joy when he is named king is expressed in a theme so rich with syncopations as to leave him (and the listeners) breathless. In almost every piece in Zelmira Rossini tries to interpret afresh the conven¬tions of his style. Particularly striking is the quality of the recitatives. The path traversed by Rossini in this area within the space of some six years, from Otello to Ermione and then to Zelmira, gives a measure of the composer's artistic growth.
The opera has public moments of solemnity, lamentation, or terror that reproduce the initial tone of dark drama, but the chromaticism also strikes more intimate chords of pathos. The duettino `Perche me guardi, e piangi', in which Zelmira entrusts her child to Emma, is one of the most pathetic moments in Rossini's work. The melodic chro¬maticism has a Bellinian aura; the accompaniment is re-duced to harp and cor anglais. In the first recitative of the second finale, when Zelmira and her son are reunited, the use of these two instruments recalls the atmosphere of the duettino and thus the touching moment of separation. Especially in the ensembles one finds pages of a refined, classical style, a celebration of the abstract power of music: the slow section of the first finale (for quintet and chorus) or the andante of the quintet perfectly exemplify this ideal of beauty.