Subtitled A Secret History of the Castrati, Lucy Powell's play is just a touch more informative than necessary. The thought particularly strikes you as you watch a puppet having its testicles removed, a decidedly unpleasant process that involves much tugging. It is no surprise to discover that the operation's mortality rates were "obscene". But Powell also has a tendency to state facts baldly and earnestly; there are moments when True or Falsetto? feels more like an animated textbook than a play.
At its best, however, this aria-strewn monologue traces the castrato's role in the development of opera with wit and an irreverent theatricality. A Bond-style baddie in the Vatican sanctions the first castration to overcome the lack of female sopranos in the choir; later there is an amusing argument between the castrati, who take pride in being "the essence of the illusion", and the composer Gluck, who wants an end to all the senseless cavorting and meaninglessly ornate singing in opera.
Ernesto Tomasini gives a wonderful performance: it is flamboyant, but also quietly communicates the sadness at the story's heart. His falsetto voice captures the chimerical sound of the castrati with eerie accuracy, something that becomes clear when we hear a scratchy recording of the last castrato, Moreschi, made at the turn of the 20th century.
He needs a director though: there are long spells when he disappears from the stage for an elaborate costume change and the play loses all its impetus. But his admiration for castrati shines through, bringing dignity to people created for art and dismissed as abominations.
· Until August 26. Box office: 0131-556 6550.
