Radamisto was among Handel's first efforts specifically to cultivate an English audience for Italian "opera seria". It was first performed in London in 1720, with at least some backing from the King, who may well have previewed the score. It's based on a libretto, already set by various composers in Italy, which was in turn based on a theatrical adaptation of a French play. Whoever adapted the story for Handel's purposes had a bit more literary sense than many of the "dear Saxon's" later librettists; the 'action' is well and clearly developed in the extended dramatic recitativos, allowing the da capo arias full freedom to be emotionally expressive without slowing down the exposition.
The story is, in fact, a trifle involuted. Radamisto and Zenobia are faithful lovers. Radamisto's sister, Polissena, is married to Tiridate, the King of Armenia, to whom she is faithful, but Tiridate is obsessed with passion for Zenobia. To make things stickier, Tiridate's brother Fraarte is also in love with Zenobia, while Tiridates' chief general Tigrane is in love with Polissena. Don't fret too much about the details; as I said, the tale becomes clear as the opera is sung. On the whole, this is one of the more tightly-plotted of Handel's operas. Apparently it was clear enough to be successful in London in 1720; it was met with loud applause, performed often, and revived in later years.
It's the two wives who emerge as heroically faithful and courageous, while the men are an unsteady lot. One could interpret the drama coherently by taking it as a parable of the restoration of the tyrant Tiridate's virtue and sanity through the example of fearless devotion set by the other characters.
But hey, it's opera, and it's all about the singing. Two mezzo-sopranos - Joyce DiDonato and Maite Beaumont - have the choicest roles as Radamisto and Zenobia, and they bring emotive gravity to their arias of desperation and devotion. The smaller roles of Polissena, Fraarte and Tigrane are all sung by flexible sopranos - Patrizia Ciofi, Dominique Labelle, and Laura Cherici. The tyrant Tiridate is sung by tenor Zachary Stains. (Isn't it nice to have the villain be a tenor for a change? We basses get that chore altogether too often!)
Basso Carlo Lepore sings the last role, as Farasmane, the father of Radamisto and Polissena. This is as fine a cast as I can imagine, all adept at the 'historically informed' vocal gymnastics required for Baroque opera.
It's almost a given that Il Complesso Barocco, under the baton of Alan Curtis, will perform flawlessly, and they do. This was probably the first opera ever staged in London to use an orchestra including trumpet and horns, as well as virtuosic oboes, along with the full complement of strings and continuo instruments. Il Complesso performs, with gusto and precision, this richly colorful score. Each act, by the way, concludes with a brief instrumental ballet -- a gesture perhaps to 18th C taste.
Radamisto is a very full-bodied opera, with arias expressing every emotion appropriate to the anxiety of the lovers: defiance, desperation, devotion; adoration, detestation, repentance, relief, and joy. There are simply no 'routine' moments of music in it. I'll venture to say it's one of Handel's masterworks.
The good news is that it's now available in the Virgin Classics bargain box of recordings by Il Complesso Barocco. The six operas in the box are:
RODRIGO - 2 CDs recorded in 1999, with Gloria Banditelli, Sandrine Piau, Roberta Invernizzi
RADAMISTO - 3 CDs 2005, with Zachary Stains, Dominique Labelle, Joyce DiDonato
ADMETO - 3 CDs 1978, with René Jacobs, James Bowman, Max von Egmond
FERNANDO - 2 CDs 2007, with Lawrence Zazzo, Max Cencic, Antonio Abete
ARMINIO - 2 CDs 2001, with Vivica Genoux, Dominique Labelle, Riccardo Ristori
DEIDAMIA - 3 CDs 2003, with Simone Kermes, Anna Bonitatibus, Furio Zanassi