Can it be nearly a quarter-century ago that an Italian mezzo-soprano in her early twenties recorded her first recital? Classical music and the recording industry have undergone remarkable changes during the intervening years, but Cecilia Bartoli remains the same passionate iconoclast who burst onto the scene with that 1988 Rossini CD. Any new Bartoli recording has become a big event, and Mission–her just-released collection of music by Agostino Steffani–proves once again that there is no one quite like Bartoli– ever the Roman conqueror!

Increasingly Bartoli’s recordings are high-concept affairs, and Mission aims to top them all, beginning with the five ersatz-mystery teaser videos made available in the months prior to the CD’s release.

Around the same time the first video appeared, the CD’s arresting black-and-white cover picturing Bartoli transformed into a bald-pated priest intensely staring at and thrusting a crucifix toward the viewer was similarly “leaked” yet no information whatsoever about the CD’s contents was announced.

Eventually the “mission” was revealed to be a re-examination of Steffani (1654-1728), an important composer heretofore more written about than performed. Decca’s typically deluxe CD hard-cover book (over 170 pages in three languages) includes no fewer than 10 short essays delving into the complex history of this transitional opera figure. The first opens with a deliberately provocative question: “Who was the greatest Italian composer between Monteverdi and Vivaldi?”

The unidentified writer puts forth obvious candidates like Cavalli, Corelli and Alessandro Scarlatti before making the case for Steffani. I remain skeptical, but Bartoli and her superb collaborators, particularly fiery Swiss conductor Diego Fasolis and his orchestra I Barocchisti, make a splendid case for Castelfranco Veneto’s favorite son.

And what might make Agostino Steffani so intriguing? One essay presents the compelling (and convincing) hypothesis that Steffani may have been a castrato! Not only a composer, he was also a priest like Vivaldi (and eventually a bishop), as well as a diplomatic envoy whose missions made him a player in some of the most important political negotiations of the time. A Roman Catholic posted to Lutheran Germany for most of his career, he worked to promote his religion in a land that had rejected it.

Bartoli’s Mission also seeks converts: she brings all her considerable searching musical intelligence and promotional acumen to a project which clearly aspires to bring The Word (and The Music) to those unfamiliar with this fascinating figure. In her thirst for maximum exposure, she has even gotten famed mystery writer (and zealous baroque opera fan) Donna Leon into the act.

In the book’s final essay “Mugged by Beauty” Leon confesses that Bartoli sent her many documents about Steffani’s complex life and neglected music. Leon then became so entranced by him that her latest novel The Jewels of Paradise (just published to coincide with the release of Mission) abandons Commissioner Brunetti and instead follows Caterina Pellegrini as she delves into the secrets contained in a recently rediscovered long-lost Steffani archive.

Although Steffani’s operas were known and admired, he was most noted during his lifetime for his chamber duets which were published and performed far beyond the German courts for which his operas were commissioned. In the early 1700s Handel who had become familiar with Steffani’s operas in Hamburg where they were performed in German translation obtained a copy of the duets which now rests in the British Library. His own scintillating duos clearly show that he learned well from his Italian predecessor.

In the early 80s American harpsichordist and conductor Alan Curtis put together a superb collection of Steffani’s duets for Archiv featuring Daniela Mazzucato, Carolyn Watkinson, Paul Esswood and John Elwes. Unfortunately the CD reissue is out of print but definitely worth searching for.

More recent recordings by soprano Monique Zanetti and countertenor Pascal Bertin and by soprano Rossana Bertini and countertenor Claudio Cavina (my favorite, along with the Curtis collection) present those sensuous multi-movement duets in their best light.

However, Steffani’s operas aren’t quite as obscure as the Bartoli machine might have one believe. Beginning in the 1970s American musicologist and conductor Newell Jenkins became a pioneer in spreading the word about Steffani. Back when 17th and 18th century opera was even more of a rarity than it is today in the US, Jenkins’s Clarion Music Society gave the modern premieres of at least five Steffani operas in concert in New York City, as well as staging several of those works in the composer’s hometown of Castelfranco Veneto.

I had recordings of three of those fine Jenkins performances which had been released on “private” LPs and was particularly taken with Tassilone and La libertà contenta. In 1987 at Alice Tully Hall, I was lucky enough to attend Jenkins’s final Steffani opera, Le rivali concordi from 1692. I remember it as a wildly uneven show yet brief glimmers of Steffani’s magic still peeked through.

Even though he didn’t present any operas after that, Jenkins included some appealing small-scale Steffani pieces in a Clarion concert I attended in the early 90s. In addition, during the first season of the ill-fated New York Collegium in 1999, its music director the late Gustav Leonhardt made a moving case for Steffani’s 1728 sacred masterpiece Stabat Mater, his final composition.

But by and large his operas remained unperformed in the US until just last year.

Recently, Niobe, Regina di Tebe has proven to be “the” Steffani opera and, prior to Mission, the key to his rediscovery. Thomas Hengelbrock conducted a revival at the 2008 Schwetzinger Festival, a production which was imported two years later by Covent Garden, starring Véronique Gens in the title role. Then in June 2011 a fully staged Steffani opera found its way onto a major American stage when the Boston Early Music Festival presented an acclaimed Niobe featuring Amanda Forsythe and superstar French countertenor Philippe Jaroussky as Anfione. Possibly due to Jaroussky’s participation, there have been rumors of a future European tour of the BEMF production along with either a CD or DVD recording.

Many opera composers of the time were itinerant wandering from country to country in search of patrons, and nearly all of Steffani’s operas premiered in Germany, primarily during his long tenures in Munich and Hanover. Unfortunately, Steffani seems to have been particularly unlucky as discussions of his works rarely appear in histories of Italian music nor do historians of German music consider him appropriate for consideration. However, recently things changed when Colin Timms published a book-length study of the composer Polymath of the Baroque in 2003.

Many of Steffani’s works also fall into a period of Italian opera which remains mostly unexplored. While operas by Cavalli continue to be regularly revived, including Gotham Chamber Opera’s upcoming production of Eliogabalo, operas by the composers following him and active during the last third of the 17th century are virtually ignored, including Alessandro Scarlatti’s over 60 works (so tirelessly promoted by musicologist Donald Jay Grout), despite the tantalizing glimpse of his final opera, 1721’s La Griselda.

So Steffani’s operas stand on the awkward bridge between those Venetian works of Cavalli and the later more formal opera seria familiar to most via Handel and his contemporaries. His numerous arias are often quite short, rarely more than two or three minutes, and do not always include a da capo repeat. They flow rather more fluidly in and out of the recitatives than in more stiffly organized opera seria. Though there is some florid writing, most are much simpler than those composed for the increasingly singer-focused operas of the 18th century.

Perhaps due to German taste (and/or possibly French influences—Steffani played for Louis XIV and met Lully and studied his works) his operas often contain choruses and dance suites—neither of which regularly appear in works written for Italian theaters. Based on its single recording, Steffani didn’t particularly excel at dance music.

Mission strives for a comprehensive overview of his work including 25 excerpts from 12 operas written over a nearly 30 year period, 1681 – 1709: Alarico il Baltha; Servio Tullio; Niobe, Regina di Tebe; Tassilone; I Trionfi del fato; Arminio; La superbia d’Alessandro; La libertà contenta; La lotta d’Hercole con Acheloo; Le rivali concordi; Henrico Leone; and Marco Aurelio. Apparently consumed by his diplomatic duties, he surprisingly wrote no operas during the final 20 years of his life.

Pieces have been carefully chosen to provide as much variety as possible, from stirring martial numbers ablaze with trumpets to the most melting of laments. The often quite sumptuous orchestration reveals in particular Steffani’s pioneering use of woodwinds. The CD notes list nearly 60 orchestra members for I Barocchisti, although I suspect that that high number might be partly due to changes in personnel during the recording period which took place over five months.

And what of Mission’s raison d’être? Steffani could scarcely ask for a more enthusiastic or accomplished advocate than Cecilia Bartoli whose passion for the music is clearly felt in every moment. Her smoky mezzo still sounds rich and plush and remarkably well preserved, though perhaps because she has increasingly sung music written for soprano, there are more pronounced register breaks than before.

She always gives 120% which can be exhausting; occasionally I would have been happy with a mere 100%. Every word, every note is shaped with such care and deliberation that I did sometimes hunger for more simplicity, spontaneity. No doubt that intensity is part of why she remains such a polarizing figure, as I suspect many listeners may find it all a bit tiring.

A long while ago someone related to me a discussion he’d overheard about dance: several Balanchine fanatics were arguing the merits of Suzanne Farrell versus Merrill Ashley, and the consensus came down to: ballerinas are either supreme in adagio (Farrell) or allegro (Ashley) but rarely both. It got me wondering whether operatic prima donnas might also be similarly categorized. Joan Sutherland, for one, has always been a singer where I eagerly to skip the cavatina to get to the cabaletta.

Contrary to her general reputation, Bartoli remains a singer whom I much prefer in adagio; the “machine-gun” coloratura racing faster than a speeding bullet through the music has nearly always rubbed me the wrong way. Based on her five 21st century NYC concerts (she hasn’t appeared in a staged opera in the US for nearly fourteen years), I suspect I may be the only one who feels that way: those wildly over-the-top florid pieces always bring down the house.

But the unorthodox method by which she produces those torrents of notes usually turns me off—“aspirated” doesn’t quite seem an adequate term, since I’ve never heard anyone else sing in quite that way. Yet I must admit that her coloratura in Mission is more legato, less “herky-jerky” than on other occasions.

But I continue to find Bartoli at her very best in slow pieces where she magically spins out long, long lines on seemingly endless threads of breath. She’s likewise admirably able to keep the listener’s interest during those arias that can be quite long, although none of the pieces on Mission compare to some featured on Sacrificium which run more than ten minutes.

Though some may criticize the occasionally attenuated tempi as self-indulgent, I remain bewitched by arias from Niobe, Regina di Tebe like “Dal mio petto” or “Ti Stringo, mio Nume” (accompanied only by solo lute) or “Deh non far colle tue lagrime” from Tassilone. The delicious ciaconna from Servio Tullio is infectiously—and simply—done, as is the quivering “Palpitanti sfere belle” from Alarico. In just two minutes, she breathes vibrant life into the tiny gem “Foschi crepuscoli” snatched from La libertà contenta. Altogether the singing strikes me as less mannered, more welcoming than on other recent projects.

A savvy decision was made to vary the program by including works with chorus (featuring Fasolis’s excellent Coro della Radiotelevsione svizzera) and four duets with Jaroussky.

Given both his participation in the recent Boston Niobe and his extremely successful recording career, the “special guest” appearance of the French countertenor is no surprise here (courtesy of Virgin Classics, of course). Yet I don’t find him a good partner for Bartoli. While Jaroussky’s ethos remains determinedly ethereal, Bartoli’s is eminently corporeal, and this clash results more in an ill-conceived mismatch rather than a fascinating juxtaposition of opposites. It also doesn’t help that Jaroussky hasn’t been singing particularly well lately.

The pairing strikes me as another example of Bartoli’s recent questionable taste in countertenors. Her choice (and, of course, one assumes it was her choice) of Andreas Scholl to be Giulio Cesare to her recent Cleopatra in Handel’s opera at the Salzburg Pfingsten Festival (for which she now serves as artistic director) also seemed a misjudgment. His reticent, aristocratic emperor jarred badly with her extravagantly voluptuous, extroverted Egyptian queen. However, she doesn’t always make the wrong choice; she has also recently performed with the extraordinary Argentinian countertenor Franco Fagioli whose flamboyant, no-holds-barred style seems much more attuned to hers.

Will Mission create a flood of new interest in Steffani?  I wonder. The pieces she’s chosen are thoroughly beguiling, yet my experience of the complete operas is that they are not consistently engrossing—many longeurs only occasionally enlivened by a marvelous moment. For example, the 16 arias of Orlando Generoso’s first act pass >by pleasantly enough yet none strike the listener as particularly memorable.

But then early in act two there’s a long scene that just knocks your socks off. Angelica sings a beautiful short da capo aria accompanied by obbligato violin; Orlando who has been eavesdropping has a short recitative followed by a strikingly similar short da capo aria for Ruggiero, this one with a yearning oboe accompaniment. Then Angelica joins Ruggiero in a repeat of his aria where the oboe and violin similarly intertwine.

Nothing in the rest of the opera reaches the heights of this blissful scene, although Orlando’s two extended mad scenes are formally interesting if not musically arresting. And over the past few years, I have doggedly listened to three different broadcasts of Niobe yet to be convinced that it’s a forgotten masterpiece—the excerpts from it that appear on Mission are indeed wonderful–but the other three (or more) hours? Not so much.

All told, I’ve never understood the violent reactions to Bartoli from the opposing sides of the operatic Colosseum: the screaming, obsessed fanatics who sell out concerts days after they’re announced nor the snarky nay-sayers who vitriolically excoriate every note, facial expression or repertoire choice. I continue to enjoy her inquisitive sensibility and stylish performing while still occasionally recoiling from her excesses.

Over the past two decades she’s clearly proven herself a uniquely charismatic performer who transcends ordinary expectations of classical music devotion. How else can one explain the likelihood that thousands and thousands of this CD will be snatched up–a disk devoted to works by a composer almost no one has heard and whose name doesn’t even appear on the front cover?