The auditorium was packed, the critics effusive and the soprano Angela Gheorghiu greeted with cheers and foot-stamping at London's Royal Opera House at the end of last year. To score a hit in times of cutbacks is always difficult, but what makes Gheorghiu's London triumph more remarkable is that it was not with a blockbuster opera but with a relatively unknown work, Franco Cilea's Adriana Lecouvreur.
While it is sometimes used as a vehicle for sopranos past their prime (among whom Gheorghiu cannot be counted) Cilea's impressive but unwieldy opera is rarely staged, in part due to its preposterous plot, a labyrinthine nightmare involving love rivalry, play acting and poisoned violets.
Its success, however, is no isolated phenomenon. Across the world's opera houses, there is a new hunger for rediscovering older operas that have fallen from favour. Following on from the fashion for baroque operas - once considered unsellable but now proving major crowd pleasers - a fresh flurry of forgotten works are being dusted off and revived, often with considerable success.
Here are some of the new-old titles currently being rediscovered.
Antigona by Tommaso Traetta
Lean, punchy and musically brilliant, this 1772 opera by the Russian empress Catherine the Great's court composer deserves to be far better known.
The Italian native Traetta's music has little of the frilly ornament we associate with his fellow countrymen, and the composer was, in fact, as influenced by French music as by that of his homeland. His version of Sophocles's tragedy is a strident, dramatically muscular affair stripped of any baroque frippery, whose early classical style recalls the dynamic brilliance of the young Mozart.
In keeping with the tastes of his time, Traetta couldn't resist giving the opera a happy ending, but otherwise there's a real brooding sense of psychological realism to the proceedings, not dissimilar to the brilliance of Traetta's better-known Viennese contemporary and fellow opera reformer, Gluck.
After languishing unknown for years, the opera finally seems to be getting a high-profile revival - Berlin's Staatsoper is staging its premiere of the work this winter from January 30.
King Roger by Karol Szymanowski
Twentieth-century operas are notorious for disappearing like the Titanic after their premieres, but this haunting work from 1924 has been dragged back up from the depths for a remarkable comeback.
While its spare plot might disappoint melodrama junkies hooked on grand opera, the Polish composer Szymanowski's music is a shimmering ray of late Romantic sunshine, both eclectic and sensuous in its blend of eastern and western influences.
A plea for cultural and religious tolerance set in mediaeval Sicily, the music's dreamy overtones recall Szymanowski's contemporaries Ravel and Scriabin, while there's also a clear Slavonic folk influence in the deep, sonorous choruses. Its celebration of pagan values makes King Roger seem quite modern - a quality that has encouraged its revival.
Following a production in Paris, King Roger appears at Madrid's Teatro Real this April.
The Huguenots by Giacomo Meyerbeer
The Huguenots was once an opera it was embarrassing to admit you hadn't seen - a hugely popular work that has received more than a thousand productions at the Paris Opera alone.
With its melodramatic plot, lavish historical setting and gorgeous, frankly decorative melodies, it helped make the German-born Jewish Meyerbeer a musical superstar in the 1830s and 1840s - one who earned the jealous loathing and poison pen of the young Wagner.
The opera's fall from grace in the 20th century is down to one problem: many companies fear that it's just too hard to stage. With its many settings and large cast of soloists, this tale of religious strife in 16th-century France is expensive to produce, while the dazzling music offers such phenomenally difficult vocal parts that casting can be a headache.
This means the opera is often staged only in concert form, though audiences will have the chance to hear its breathtaking set pieces in a full production at the Théâtre Royal de la Monnaie in Brussels in June, with musical direction from the excellent Marc Minkowski.
Attila by Verdi
How could an opera from a composer as popular as Verdi ever fall out of the regular repertoire? It may almost beggar belief, but the composer's Attila only had its American premiere in 2007, with the production repeated last year at New York's Met Opera.
Despite an impressive score, it's not hard to find the culprit for this disappearing act - Attila's gung-ho nationalist plot needs some serious tweaking to resonate with non-Italians. The story of early Italians fighting off an invasion from Attila, king of the Huns, the opera must have touched a nerve at its 1846 premiere in Venice, when the city was still occupied by Austrian forces.
More recently, however, its story inevitably means less to international audiences. That's no reason to avoid the opera however - its plot is far more interesting than Verdi's more popular but completely nonsensical Il Trovatore and it's still full of the sort of dramatically charged, show-stopping arias that make Verdi's work as a whole so thrilling.
Montezuma by Carl Heinrich Graun
Few people would expect an operatic collaboration between a Prussian king and his now obscure court composer to be more than a pompous hash, but this sprightly mid-18th-century opera is actually a minor delight.
With a scenario written by the philosopher king Frederick the Great, this story of the Spanish conquest of Mexico comes down firmly on the side of the defeated Aztecs, providing a surprisingly harsh critique of western intervention for a European ruler who spent half his life invading his neighbours.
The music, written by Frederick's official composer Graun, comes from that interesting but little-known overlapping period between the baroque and the classical. Despite the hefty subject matter, the score is often charming, with juicy soprano parts that offer their singers a chance to show off their dexterity on fast runs and trills.
Though little performed, Montezuma was staged last year at Madrid's Teatro Real and the Edinburgh Festival.
La Cenerentola by Gioachino Rossini
Now one of the most popular works in the repertoire, it's hard to believe that this frothy 1817 version of the Cinderella story was once considered a musical dinosaur. A major success in its early years, its combination of wonderful melodies and show-off musical pyrotechnics should have kept it a popular crowd-pleaser.
Its fall from grace lay in the difficulty of casting the main role, Cinderella, who is usually imagined as a wispy slip of a girl, but was written by Rossini as a contralto, the lowest female voice in the operatic register. As this type of voice was less commonly trained-up for most of the 20th century, Rossini's opera had to wait for a new generation of contraltos and mezzo sopranos from the 1960s onwards to bring La Cenerentola back into vogue.
Even today, contraltos are often stuck playing wicked characters, or parts formerly reserved for castrati, but coloratura mezzos such as Cecilia Bartoli have given Rossini's opera a new lease on life, their deeper voices perfectly designed to flesh out Cinderella's jaw-dropping vocal runs.
