King of the high Cs: it's a handy pun. But why are operatic high Cs such a big deal? The high C - actually, any inordinately high note sung long and loud - has a mystique all its own. Watching the Peruvian tenor Juan Diego Florez soaring through the nine Cs of the show-stopping aria "Ah, mes amis" in Donizetti's La fille du régiment at Covent Garden recently, I couldn't help thinking that it's about adrenaline. We're pre-programmed to respond to high, loud noises with that old fight-or-flight instinct, an adrenaline rush. A tenor's top notes, however refined, still provoke it. All he has to do is stand and deliver them, and the public goes bananas.
Verdi's romantic blockbuster Il trovatore, currently showing at the Royal Opera House, features one of the most famous high Cs of the lot, in the aria "Di quella pira". "There's something apparently superhuman about a tenor singing a long, high note," comments Marcelo Alvarez, the barrel-chested Argentinian tenor who's singing it in the role of the troubadour Manrico. "Everyone responds to this astonishing sound that they feel they'll never be able to make themselves."
Sometimes, though, the public goes a lot more bananas if the tenor misses. "Singing the high notes is enjoyable as long as it's easy," Florez tells me. "But it's not nice if you go to a performance and you hear someone struggling for that note." And certain audiences like to express themselves on this subject more forcibly than others - notably at La Scala, Milan.
Alvarez once fell foul of the booers at La Scala, allegedly because he didn't quite get a top note. He attributes the incident to a variety of other factors: "The audience there, if it doesn't like a production, often waits until the radio broadcast to make its feelings known on air," he declares. "Besides, in such cases it's only a tiny handful of people who are booing while many more clap and cheer, but of course it's the boos that make news."
But in December, the tenor Roberto Alagna made the news in a big way when he walked off the La Scala stage during the first act of Aida after his aria "Celeste Aida" was booed. He refused to go back. The combination of below-par performance and way-below-par behaviour led to the kind of virulent row that can only happen in opera: threatened lock-outs, law-suits and mud-slinging from everybody from the director Franco Zeffirelli ("Radames isn't exactly a role tailor-made for him") to the ballet dancer Roberto Bolle, who appeared as a slave in a gold thong ("I realise Alagna envies my body").
Many suggested that Alagna - who declared that the trauma of being booed had brought on hypoglycaemia - just didn't have the right voice for the role. Few were impressed by the handful of bars he sang, very quietly and into a microphone, in a subsequent television interview. "In the present market, a true Radames does not exist, so it's useless to search," declared Zeffirelli, interviewed in Il Giornale. "We have plenty of baritones, mezzos, but there's such a lack of dramatic tenors. In fact, nobody stages Il trovatore any more, because we live in the world where you don't have the singers for that kind of role."
In Mozart's day, tenors weren't supposed to belt out top level top notes like this. His tenor roles, like Tamino in Die Zauberflöte or Don Ottavio in Don Giovanni, are restrained, noble and rather elegant; plenty of singers have considered Don Ottavio the wrong side of wimpish. Beethoven's Florestan in Fidelio is dramatic, but never for the sake of it. So, was tenore molto con belto an Italian invention? Not quite - the first tenor to perform a high C with a full "chest" voice, Florez tells me, was actually a French tenor named Gilbert Duprez (1806-1896). "Before that, it was produced in a softer way, with a head voice," he adds, "and when Duprez first began to sing like this, some people were shocked, including Rossini, who didn't like it. But then it became the fashionable way to sing, because the public said: 'Wow, what a sound!'"
Those notes have to arrive more or less naturally, or not at all. For the lyric or leggiero tenor (the tenors with the highest voices on the fach scale) - singers like Luciano Pavarotti and Florez - they're a piece of cake. Lower-voiced dramatic tenors, though, have always had a harder time of it. High notes weren't on the menu for Enrico Caruso, the most revered tenor in history, who once warned Puccini himself not to expect him to sing the high C in La bohème. Caruso's tone was dark and baritonal, though he worked hard for the upper register. Today, Placido Domingo is among the tenors in the same boat. When I interviewed him in the summer of 2005, Domingo told me that he "wasn't a natural tenor" and has always had to work hard to keep his range in shape. Now, in his mid-sixties, he's about to go further, coming out as a full-fledged baritone in one of Verdi's biggest creations for this voice, the title role in Simon Boccanegra. He's scheduled to sing it in London in the 2009-10 season.
Pavarotti in his heyday was another matter. The original "king of the high Cs", he stunned Covent Garden audiences 40 years ago with that famous aria in La fille du regiment and has never looked back. It's interesting that while Domingo is one of the most multi-talented stars in the musical world - being singer, conductor, opera house director and consummate actor in one - Pavarotti isn't. He's never done much except sing, his operatic repertoire has never been as broad as Domingo's and his physical size has sometimes handicapped his acting; yet when the high notes emerged, the rest didn't matter any more. Pavarotti, though, also got booed at La Scala when he cracked a top note. His reputation recovered; whether more recent victims will do so isn't yet clear.
The high notes syndrome isn't limited to tenors. The role that can kill off a high soprano is the Queen of the Night in Mozart's Die Zauberflöte. Plenty of singers have made their names in the role - Edita Gruberova, Sumi Jo and Diana Damrau are some of the best - but you only had to see Maureen Lipman's recreation of the ear-crinkling Florence Foster-Jenkins, the wealthy would-be soprano of the 1930s and 1940s, in Peter Quilter's play Glorious! to realise just how dreadful the famous aria could sound. Foster-Jenkins had a cult following all her own, but it was said that when Caruso heard her he said he'd "never heard anything like it" - once you've heard her, you know what he meant.
At best, effortlessness - or at least an illusion of it - is required in sopranos' high notes every bit as much as in tenors'. Natalie Dessay, the French soprano who's just starred opposite Florez in the high-set role of Marie in La fille du regiment at Covent Garden, declares: "High notes are a pleasure. It's a game. It's almost like a drug - being 'high'! You know the audience likes it, you can do it and you do it because it's natural. It's as if you offer something very beautiful to somebody and you know it will be appreciated."
It's a little ironic that, while the top notes get the top ovations, for the singers who really have the voice for them they're not the hardest part of the show - nor even the most rewarding. "When I sang my very first Manrico in Parma last season, I had a wonderful response after 'Di quella pira' and I was very pleased to hear an enthusiastic reaction from this difficult audience," Alvarez recounts. "What gave me even more satisfaction, though, was what happened in the opera's final scene." During a particularly impassioned phrase in the last duet, Alvarez took the volume down instead of up. "Someone in the audience shouted 'grazie'. This one expression of thanks meant more to me than the whole audience screaming 'bravo' at the end of 'Di quella pira'. It meant so much to me to know that they had understood what I was trying to communicate.
"Later, people actually thanked me for 'helping them discover the fourth act' of Il trovatore, in which the duet between Manrico and Azucena is perhaps the best music in the opera. Too often they hadn't looked beyond the big note in 'Di quella pira', although it arrives at a rather emotionally silly moment in the story. When you know that the audience has 'got' what you are trying to achieve, it makes it all worth it," he says. "I guess that's what singing is really all about."
'Il trovatore' is at the Royal Opera House, London WC1 ( www.royaloperahouse.org; 020-7304 4000) to 23 FebruaryReuse content