The Piano Tuner, Linbury Studio, Royal Opera House, London

It's a meaty metaphor that Daniel Mason serves up in his 2002 novel The Piano Tuner. You can see how it might appeal to a composer such as Nigel Osborne. The character that he and his librettist Amanda Holden have come to know and, quite clearly, to love in their opera of the same name is Edgar Drake, a respected piano tuner, purveyor of good vibrations, a man with the potential to make universal harmony of one true pitch.

It's a meaty metaphor that Daniel Mason serves up in his 2002 novel The Piano Tuner. You can see how it might appeal to a composer such as Nigel Osborne. The character that he and his librettist Amanda Holden have come to know and, quite clearly, to love in their opera of the same name is Edgar Drake, a respected piano tuner, purveyor of good vibrations, a man with the potential to make universal harmony of one true pitch.

We meet him at the very top of the opera voicing his way through the process, the ritual, the labour of love that is tuning a fine piano. The director (Michael McCarthy) and designer (Simon Banham) of this Music Theatre Wales world premiere effectively place him and us inside the piano. The thrust stage is divided floor to ceiling by the strings that sing: on one side lies the chamber orchestra, on the other, places unknown accessed only through this forest of strings. A deep resonance of string bass is countered by the exotic chime of glockenspiel. Edgar's journey begins with the words: "Music enters the unconscious, carries us away/ overwhelms beyond the realms/ where human fingers play."

The music that carries Edgar away makes capital of the art of fugue and its equivalent in psychiatry, where the word can be used to convey the disturbed state of mind that may afflict the amnesiac patient who has disappeared from home. Edgar's own disappearance begins with a request to the British government that he be urgently despatched to Mae Lwin, an outpost of Burma, just after the Anglo-Burmese war. There, an eccentric military doctor, Anthony Carroll, needs an expert to tune his grand piano. Its music may bring harmony to the troubled region.

And so begins Edgar's odyssey - and the metaphor at its purest: the power of music as healer. Immediately upon Edgar's arrival in Mae Lwin, Osborne and Holden pointedly juxtapose his rapturous first encounter with the "injured" piano with Dr Carroll's roll call of local ailments. The naming of these unpleasant diseases is underscored at one point by a beautiful little fugato in two violins. The point is deftly made. And the point is that this beautiful corner of the world has been colonised, its ancient culture corrupted, by those who would reinvent it to their own ends and in their own image.

Osborne does well to convey as much as he does in sound alone. The transformation of his ensemble from Western to Eastern colours, from the dry, academic agitatos of his opening act to the seductive slides and percussive chimes of this distant "paradise", is well engineered. Two Thai musicians enrich the ethnic tinta of the music, their instruments used as a kind of extension of the Western instruments, like the harp and oboe, whose timbres Osborne has coarsened very effectively.

Vocally, too, the exotic melismas of the native girl Khin Myo (the excellent Donna Bateman), to whom Edgar is so drawn, emerge like a seductive synthesis of the region's song, both human and animal. In one striking moment, Osborne transfers this melancholic siren song from the girl to Edgar's wife. What one has gained, the other has lost.

The trouble is that The Piano Tuner is a drama of ideas and sensations more than actions, and while the simple ethnicity of this staging - involving puppets and dance - remains true to its essence, it is not hard to imagine it better done. Only then - and despite the best efforts of this small ensemble with commanding central performances from Giles Davies as Edgar Drake and Steven Gallop as Dr Anthony Carroll - will we be able to gauge fully its success or failure.

Still, some points are well made. As the region at the heart of the drama is destabilised and the government looks to apportion blame, Edgar exclaims: "I am shocked that British intelligence can leap to such stupid conclusions!" Ouch.

Touring to 24 November (029 2049 8471)