“A Zeffirelli, dopo le polemiche della vigilia che lo hanno opposto al soprano Daniela Dessì, da lui ritenuta non giusta per il ruolo di Violetta in questa Traviata, qualche dissenso misto agli applausi al momento di comparire in proscenio assieme a Gelmetti.” [Il Messaggero]

On the other hand, maybe the dissenters were disgruntled canary fanciers?

On 18 December 2009, the opening night of the production, there was no ‘high E flat’. In the Rome theatre, Zeffirelli’s foes were immediately ready to point out that to please the director, second-choice singers had been hired.