Robert Lepage has crammed his grand theatrical imagination into a diminutive form - the song cycle.
The French-Canadian theatre director Robert Lepage thinks big, and expects his audiences to do likewise. In 1996 he reduced Hamlet to a solo show, Elsinore, with Lepage himself the soloist. The Dragon's Trilogy, his account of Chinese immigrations to Canada (seen in London in 1987), lasted some six hours, a duration topped by The Seven Dreams of the River Ota, which, when Lepage brought its final version to the National Theatre in 1996, lasted close to eight hours.

Yet thinking big does not necessarily result in epics that occupy most of the waking day. His latest project is a production of Mahler's song- cycle Kindertotenlieder, a piece lasting an epigrammatic 25 minutes. Lepage has provided theatrical action that yields a dramatic context for Mahler's five songs, which deal with a father's feelings about his children, who have died. Lepage is not the first to stage song-cycles intended for the recital platform, but such stagings remain rare, and controversial: if these composers had wanted a staging, the argument goes, they would have written an opera.

Well, yes; but by the same token, if Friedrich Ruckert, the poet who provided Mahler's texts, had wanted his poems set to music, he would have asked a composer himself. Instead, his poems had to wait 70 years for Mahler's music. If Mahler added something to Ruckert, might not Lepage add something to both? In any case, for many people the solo song recital is the least communicative of musical idioms, the singer standing stiffly by the piano trying hard to avoid all dramatic gestures when so often the music demands physical reaction.

For a director whose work thrives on sweeping dramatic gestures, Lepage came relatively late to opera, the form that his Kindertotenlieder most closely resembles. As he recalls, "I'd been asked many times. Various people wanted me to stage Wagner's Ring cycle. I'd say, 'Whoa, wait a minute. I've never directed an opera, and you want me to start with the Ring? If you can come up with something intimate, that has no chorus, then I'll be interested.' Then in 1993 Canadian Opera suggested that I do a double bill of Schoenberg's Erwartung, with one singer, and Bartok's Bluebeard's Castle, which has two. That allowed me to work very intimately with the singers, and it was fantastic."

The singer with whom Lepage worked on Erwartung was Rebecca Blankenship, and so productive was their working relationship that the two are now fully-fledged collaborators, Blankenship being co-author of both The Seven Dreams of the River Ota, and Kindertotenlieder (which she also sings).

Blankenship recalls, "We met at a point when I was discontented with opera and the narrow path I saw ahead. The higher you go, the more you realise that you'll be doing the same ten roles for the next 20 years. I still adore opera, but you're confined to a story that has to be told the way it's written. A song-cycle like Kindertotenlieder offers strong themes, which allow you to tell your own story in relationship to those themes, to find out how they apply to your life."

At the Lyric, Blankenship will sing Mahler in German, while surtitles will give, not exactly translations, but versions of Ruckert's texts, specially provided by Blake Morrison, whose other works includes a book about the James Bulger murder, As If. Although both Blankenship and Lepage are at pains to insist that they're not out to "contemporarise" Mahler, they acknowledge that Kindertotenlieder has powerful resonances for an age obsessed with children's innocence and death. The staging includes a part for a ten-year-old child, whose contribution to proceedings Lepage calls "the pretext of the narrative".

"Pretext" here is, literally, a text that comes before. Lepage explains, "Mahler specifically indicates that you shouldn't separate the songs: they take strength from their attachment to the other songs in the cycle. So we needed to find a resonance without staging the songs one by one in some kind of 'modern' context. What interested us was the craft of telling a story via the theatricality of music. Mahler lived in a time when losing a child was something you dealt with more often them we do today, and Ruckert, who lost two children, wrote 425 Kindertotenlieder. We didn't say, 'OK, what do we want to say about that?' then sit down and write it, but we've created a kind of spoken preamble. It's about Mahler, and it isn't about Mahler, and it's done very simply. Whatever form the work we do takes, we glue together forms of expression, trying to make them coherent, but it's not without clumsiness. We have to avoid being too slick, because then the audience doesn't get the impression of something alive, growing."

"This isn't an operatic piece, but it takes on an operatic feeling. I really sense theatre is becoming more operatic, and I'm more comfortable working with singers than with actors.

"I've learnt a lot from opera, from working with Rebecca. It was a big shock to discover that, on the first day of work on an opera, even if the singer is not yet involved emotionally, and remains very technical in the singing, there is all this emotion which the music conveys. That's your subtext, and it means you're starting a few steps ahead of the point at which you start in theatre. The musical text is full of indications of what emotion this should convey, and the craft of the singer is to use that information and make something of their own.

"The closest I've come to that in the theatre is doing Shakespeare, but in this century the lyrical approach to acting has been abandoned. If you listen to recordings that Sarah Bernhardt made at the beginning of the century, you hear her delivering text in a lyrical, sung way. People laugh at it now, but there's a power and a poetry in that which we have discarded."

To 30 May. Lyric Theatre,

Hammersmith (0181 741 2311)