The human voice is the most beguiling instrument, endlessly sending out messages about identity and communication. Out of this commonplace, Robert Lepage and his Quebec-based Ex Machina theatre company have produced a nine-hour, nine-story marathon of glittering brilliance and surprising longueurs.

Star rating ****

The human voice is the most beguiling instrument, endlessly sending out messages about identity and communication. Out of this commonplace, Robert Lepage and his Quebec-based Ex Machina theatre company have produced a nine-hour, nine-story marathon of glittering brilliance and surprising longueurs.

Sadly, extension does not always mean progression. Lipsynch has grown from its original three hours in Quebec through five hours at Northern Stage in Newcastle in 2007 to its present length. Lepage remains, for many of us, the greatest theatrical inventor amd showman of our age, his mastery of technical and narrative story-telling second to none.

The worlds, images and atmospheres he creates are unique and make our UK-bred iconoclast, Katie Mitchell's work in deconstruction and cinematic and theatrical convergence seem like a smaller echo of his vaster canvases.

But his additional strength - the open-endedness that allows every production a constant state of growth - has here become a weakness.

In a story that ranges across 70 years, two continents, is spoken in French, German, Spanish and English and explores a multitude of vocal effects - from opera singing to brain-damage, dubbing to recapturing memory through sound identification, each within a personal story starting with the death of a young Nicaraguan prostitute on a flight from Frankfurt to Montreal - we are treated to wonderful individual moments but often lack a sense of the relationship of each to each.

It ends, however, on a magnificent note dedicated to all young women trafficked into prostitution - Lupe (Nuria Garcia), the original young mother caught in the arms of Rebecca Blankenship's opera singing Ada (who adopted her baby), then held, Pietà-like in the arms of Jeremy (Rick Miller), her grown-up son.

Flawed it may be, but Lipsynch remains unmatchable in its artistry and compassion.