We are used to thinking of ‘opera singer’ as a profession. But no such profession existed when opera emerged as a genre at the turn of the sixteenth and seventeenth centuries, when the first public opera house opened in Venice in 1637, or for three or four decades after that: operas were too few to occupy most of anyone's time. In the early seventeenth century not even ‘singer’ was as yet a clearly defined trade. Many singers were also instrumentalists: some accompanied themselves (and some also composed their own music), while others switched between singing and playing; the commonest Italian term for them all was musici. Others again were actors or actresses who could sing, like Virginia Andreini, drafted in an emergency to create the title part in Monteverdi's Arianna of 1608.

So says Othello, confronting Iago for the last time in Shakespeare's play. He looks down to seek for the cloven hoof of a demon, for only if lago is satanic can Othello understand what has come to pass. Looking down – the physical gesture – represents an impulse to interpret, to find clues, codes, signs there in the darkness. But Iago is no supernatural being: ‘that's a fable’. What remains is an enigmatic lago more frightening than any demon – the attempt to interpret undermined by the sign not given.

‘Librettology’ has begun to acquire a working vocabulary. Critics now investigate the relationship between a libretto and its literary source in terms other than fidelity; a text adapted for musical setting no longer disappears from the realm of the ‘literary’. Historians and musicologists are considering the role of opera librettos in cultural history, with special attention to librettos that rework historical, national or mythic themes. How operatic texts transpose and thus ‘re-accent’ a nation's literary classics is emerging as a fruitful and still unexplored field.

All Puccini's biographers tell the story of how the eighteen-year-old composer, in the company of two friends, walked the nineteen miles from Lucca to Pisa to hear Verdi's latest opera, Aida; and how the impact of that opera – the first that he had ever seen performed – was such that he determined from that moment on to make a career as a composer for the theatre.