But Jessye Norman - not a mezzo but with enough weight and depth of colour in the voice to hunt on mezzo territory - does sing Phaedra. And she performed it twice this week, with Sir Colin Davis and the LSO as part of an on-going series.
Norman's Phaedra is a fiercer, more indignant personality than Baker's, and her diction isn't so precise or so intelligent. The crystal clarity of Robert Lowell's English text dissolves into a billowing vocalise devoid of consonants. But in the grandeur stakes, Ms Norman wins hands down. You feel what a terrifying ordeal it must be for poor Hippolytus to be loved by this (as Lowell has it) 'monster'. And although I doubt if monstrosity was quite what Britten envisaged, no one who can invest a mezza voce with the dramatic intensity of which Ms Norman is capable deserves anything but respect.
In the second half she sang the closing scene from Richard Strauss's Capriccio, which was like following a Stilton supper with whipped cream meringue - undeniably impressive if en route to the grotesque. But I'm bound to add that the very best moments of this programme came when Ms Norman didn't sing at all: when the orchestra filled in with Strauss's Don Juan and Britten's 'Sea Interludes' from Peter Grimes. There is an awesome chemistry at work these days between the LSO and Colin Davis: an interaction between the orchestra's powerhouse American dynamism (with a virtuosic, forward-thrusting brass sound) and Davis's English-cerebral reflectiveness (pipe-chewing, seer-like, but with an ultimately sound and penetrative mind). The Don Juan was especially magnificent: although there are no Strauss events planned for when Davis becomes Principal Conductor in 1995, a symphonic poem series is something the LSO really should consider.
The BBC SO has a different kind of virtuosity to the LSO: less glamorous, more workmanlike, and rarely better heard than in the concert performance of Berg's Lulu at the Festival Hall last weekend. It was a massive undertaking with a long and technically demanding score, but Andrew Davis brought it off with his usual panache. And although Lulu doesn't lend itself to the sort of evening dress semi-staging that was attempted here - the movements are too complicated, and with doubled roles sung in the original German it all got terribly confusing - the cast was wonderfully resilient. Patricia Wise proved why she is considered the outstanding Lulu of our times, and Jane Henschel's Countess Geschwitz was beautifully done.
But she wasn't so ideal the next night, when she appeared as the fortune-teller in Covent Garden's Ballo in Maschera revival. Her big scene was a mite too close to vaudeville, and John Cox's creakily conventional production didn't help. But there are good things in this Ballo, including a dazzling Royal Opera debut from the Russian soprano Nina Rautio as Amelia: a voice charged with a cutting, Slavic edge and all the weight required for full-blown Verdian power. There is a forceful Verdian presence in the pit, too, in Daniele Gatti, the most impressive of the new generation of Italian conductors. And if Dennis O'Neill's Gustavus lacks charisma - I wish he wouldn't sing quite so persistently into the prompt box - at least it's punchy and conscientious.
The week's disappointment was Mark Swartzentruber, a young American pianist whose debut recording (Schubert sonatas on Sony) promised more than he delivered live at the Wigmore Hall on Monday. He has interesting ideas about rooting keyboard textures in a strong, assertive bass; but at the Wigmore he seemed ill at ease and under-energised.
The week's surprise was Cesar Franck's profoundly obscure opera Hulda, which the semi-pro University College Opera resurrected at the Bloomsbury Theatre. It was advertised as the world premiere of the uncut version; to anyone familiar with received wisdom on the piece - that even in its cut state it was long and tiresome - this would have been no encouragement. Franck's metier was instrumental music: he was not a natural dramatist. But Hulda turned out to be better than its reputation. If David Drummond (the conductor-detective who tracked down the excised bits of the score) hadn't been quite so thorough it would have been better still. I could have happily surrendered half an hour of running time.
But otherwise it was a find: a post-Wagnerian essay on Nordic myth of the rape-and-pillage kind, featuring violent death at 10-minute intervals to music that sails blithely through. Close your eyes and it could be La Boheme for all the score does to signal what's going on - understandably a problem for Hulda's early critics. But with hindsight, I think it's not too fanciful to read the oblique passivity of Hulda as a sort of missing link between Wagner and Debussy. Ears attuned to Pelleas's dramaturgy shouldn't find it too much of an effort. And UCO's simple, direct staging was effective, despite the mistake of putting the chorus in latex stocking masks. These were meant to suggest the skeletal figure in Edvard Munch's The Scream, but looked more like fun-wear for suburban bondage parties.
With some promising young voices - Adele Paxton as Hulda and a bright vibrant soprano, Jane Webster, in one of the lesser roles - this was a creditable addition to UCO's track record of conjuring productions of rare operas out of little more than practical determination. And practicality presumably explains why UCO relocated Hulda to an Ibsenesque fishing community where people go barefoot: always a useful economy in low-budget shows.
'Ballo in Maschera' continues at Covent Garden, WC2 (071-240 1066) Mon & Thurs.