Two operas in one month are a turn-up indeed for admirers of the most worldly of the Bach clan. Premiered at the King’s Theatre in 1763, Zanaida was Johann Christian’s second opera seria for London and sealed his decision to make his home there. Its autograph manuscript was presumed lost until it surfaced in the library of an American collector in 2010. The following summer a staging was arranged at the Leipzig Bachfest, from which this world premiere recording is taken.

Capitalising on the craze for oriental exoticism, the King’s Theatre’s house poet Bottarelli adapted a Metastasio libretto on the dynastic and amorous rivalries between the Persians and Ottoman Turks. While the Turkish Princess Zanaida is a model of opera seria feminine forbearance, most of the other principals are ruthless psychopaths. Not that you’d guess it from Bach’s unfailingly euphonious music. Expressions of despair and overweening ambition prompt gracious minuets. Tamasse forces the unlovely Osira to witness Zanaida’s execution in a genial hunting-style aria. And so on.

Still, if you treat Zanaida as a vocal concert and forget the drama, there is plenty to enjoy here, not least the colourful, sensuous writing for woodwind (including clarinets) for which Bach became renowned. A cast featuring five sopranos, several of them sounding virtually alike, is never ideal on disc. But while there are no outstanding voices (and words are too often vague), all sing with spirit and a fair sense of style. Best are Sara Hershkowitz as Zanaida and the vibrant mezzo Marina De Liso as the sadistic Tamasse. David Stern paces the opera convincingly and gets some lively, pointed playing from his cosmopolitan period band.

Bach’s last opera, Amadis de Gaule, is a very different proposition: a tragédie lyrique composed for Paris in 1778-79, on an adaptation of the Quinault libretto set by Lully a century earlier. Parisian audiences, riven between supporters of Gluck and of Piccinni, were less than enchanted. By then the plot, a medieval farrago of chivalry and evil sorcerers, must have seemed both static and absurd. But while a modern staging of Amadis would challenge any producer, the best of Bach’s music, much of it in minor keys, rivals Gluck in its pithy intensity.

In the French tradition, the orchestra is used throughout, with a fluid intermingling of recitative, aria and chorus, plus colourful ballet numbers for dance-mad Paris. Bach is at his most lyrically alluring in, say, the Act 1 duet for the estranged lovers Amadis and Oriane, and the choruses of enchanteurs. But the explosive solos and duets for the sorcerers Arcalaüs (who spends the entire opera hyperventilating) and Arcabonne, and the eerie ghost scene, balefully coloured with trombones, will surprise anyone who views Johann Christian as an upmarket purveyor of suave galanterie.

In this first complete recording of Amadis in French, Didier Talpain directs his Czech-Slovak period orchestra with real dramatic flair. Bach’s Gluckian ostinatos crackle and spit as one scene tumbles urgently into the next. The predominantly Francophone cast all do well, not least in their expressive declamation of the recitatives. The incisive-toned Pierre-Yves Pruvot and Hjördis Thébault, clean and confident in attack, impassioned in her suicide scene, make a splendidly vivid pair of sorcerers. Tenor Philippe Do, if slightly raw in tone, skilfully negotiates the cruelly high tessitura of Amadis’s role, while Katia Velletaz has both the fire and the tenderness for Oriane’s music, not least her eloquent, Gluckian soliloquies in Act 3. The packaging is luxurious, with the discs fitted into a hardback book containing the full libretto, several well-translated essays and reproductions of contemporary prints and engravings. JC Bach fans, and indeed anyone who loves Gluck’s French operas, should snap this up.