Something clicked the other night while I watched Monteverdi’s Return of Ulysses at the Young Vic: for all the brilliance of the staging – which certainly was brilliant – it was the words that were really doing it for me.

Musicians talk of Monteverdi’s intense connection to text – the way words shaped every nuance of his music. No wonder the score for Ulysses felt so much less idiomatic and so much more contemporary delivered in English – particularly in a translation (by Christopher Cowell) that was unobtrusively effective enough to dismiss all the ‘issues’ of text-versus-music-versus-translation-versus-surtitles and so on. What came out of mouths and instruments felt like a single sonic entity – exactly how Monteverdi conceived it. You could hear every word in the small auditorium, and conductor Jonathan Cohen shaped the music with speech-like verve, urgency and colour.

If I could revive Monteverdi for three hours and give him an artistic experience 2011-style, I’d take him to see London Road, which has just opened at the National Theatre. This is a show which creates music from the speech intonations and rhythms of people from a particular localised community – that rocked by the serial killings in Ipswich in 2006.

The results are unprecedented and difficult to describe, but they seem to fuse techniques from ‘verbatim’ theatre with a number of those explored in Steve Reich’s Different Trains and Jonathan Harvey’s Speakings. Composer (Adam Cork) and lyricist (Alecky Blythe) take extended passages from group interviews and implant them sonically unchanged into a musical score – pauses, stutters, incorrect verb declensions and nuances of contemporary East Anglian speech included.

At the music’s height, ostinatos mapped on these interview passages are layered over one another, stylised music created from the resulting patterns that takes its lead variously from Disco, R‘n’B, Christmas Carols and Britten (there’s an uncanny resemblance in one scene to his East Anglian opera Albert Herring). Untrained voices deliver this polyphonic tapestry with acute skill; musical ‘numbers’ often begin with speech and for the audience it’s almost impossible to tell if and when that speech ‘becomes’ song – and vice versa.

London Road is bold and ultimately respectful of its delicate subject matter. Sometimes the music is so ingeniously built that it seems to be scarcely there at all. Cork says it’s not a musical, and he’d be unlikely to describe it as an opera. But it seems to me a game-changer for the centuries-old tradition of intertwining text and music. Anyone interested in word setting could well be wracking their brains for days after seeing London Road, trying to come to terms with what Blythe and Cork have done. I was – to the extent that I went straight to the box office to book another ticket.