Going to see living operatic legends is a risky business. You hope to breathe in a lungful of the essence of past greatness, while knowing that the voice may simply no longer be up to the job. Coming to Berlin to see Edita Gruberová sing Norma in concert at Deutsche Oper, I was given “rather you than me” warnings from various quarters: this is, after all, a soprano close to her 70th birthday singing a celebratedly difficult role.

Bellini makes you wait for Norma’s entrance: there’s a substantial overture with many of the opera's melodies, Oroveso’s “Ite sul colle,” two druid choruses and Pollione’s fine cavatina “Meco al altar di Venere.” The orchestra, conducted by Peter Valentovic, were to be very solid through the evening, but the overture did not start well, with timing slightly off and phrases tending to lose their last notes. Things improved, however, with Marko Mimica’s Oroveso, who sung “Ite sul colle” in a tightly focussed bass voice, with clarity and authority. Fabio Sartori was an excellent Pollione, a big man throwing a big voice at the role, with nicely arced phrasing, an excellent passaggio and a total lack of fear in hitting the climactic high notes. The chorus and brass combined wonderfully in the processional “Norma viene,” blending to be almost like a church organ.

Norma’s entry, when it comes, leaves nowhere for the soprano to hide: she must negotiate the most dramatic of recitatives “Sediziose voci” and Bellini’s most famous aria, “Casta diva”. The recitative showed Gruberová at her compellingly dramatic best: every syllable of the Italian was crystal clear and infused with authority: we in the audience quailed as the druids did, chastised for pursuing a rebellion that must undoubtedly fail. In “Casta diva,” however, Gruberová’s voice showed its age. The timbre is still good and she hit all the high notes, but without real confidence. In both the lead-in to high notes and in rapid runs, she resorted to sliding the notes into each other rather than articulating each note clearly.

But with the mountain of “Casta Diva” out of the way, Gruberová got better and better, and the stardust rubbed off on every duet partner. Sparks flew in her confrontations with Pollione, and her duet with Sonia Ganassi’s Adalgisa was a masterpiece of characterisation: Gruberová at her most motherly, Ganassi combining innocence and passion. The scene contains one of opera’s great “oops” moments, when Norma has just released Adalgisa from her vows so that she can be with her lover and asks sweetly “so who is the young man, then” (it is, of course, Pollione, the father of her children) – it was executed with superb black humour.

I probably wouldn’t wish to admit this face to face to an opera director, but seeing Norma in concert is a wonderful thing. Freed from the need to worry about the complexities of an inevitable “make it relevant to our times” interpretation, one can simply focus on the way Bellini infuses beauty and drama into every line of the music. In this opera, I would argue, Bellini combines the two more brilliantly than anyone before or since. The duets are what make Norma stand out, and last night’s cast sang each one superbly. The blend of voices between Sartori and Ganassi was perfectly balanced in “Va’, crudele,” while Ganassi and Gruberová’s sensitivity to each other was especially remarkable in Act II.

After the uncertain beginning, Valentovic didn’t put a foot wrong in tempi, phrasing and in allowing Bellini’s delicious woodwind and brass interventions to shine: for a composer whose orchestration is often derided, Norma’s use of orchestral forces is surprisingly varied. Valentovic was not immune, however, to the usual problems of opera in concert: when there's no orchestra pit, it’s hard for the orchestra to keep the levels down to avoid swamping the singers. Deutsche Oper exacerbated this by using a very full orchestral line-up: thinning down the number of string players might have made things easier.

One might normally come to Norma for the thrill of “Casta diva”. Here was a performance in which that big moment was uncertain, but in which almost everything else left me convinced of what a great opera this is – and of what a great artist Edita Gruberová remains in spite of age taking its toll. I can’t wait for September, when Norma returns to Covent Garden nearly two decades after last being staged there – with Ganassi in the cast.