Y Tŵr, MTW, Sherman Theatre, Cardiff

Until yesterday my only experience of the Welsh language in the opera house was a few isolated passages in Iain Bell’s In Parenthesis last year and the surtitles WNO routinely put up alongside the English in the Millennium Centre.

Now Guto Puw, a 46-year-old composer from north Wales, has written an entire opera for Music Theatre Wales and the Carmarthen-based Theatr Genedlaethol in this beautiful language of which I’m ashamed to say I know not a single word apart from a handful of road signs and the unexpected pepperings of English (“Electric – Price – Bloody Job” was one whole phrase I caught) that prove the language’s antiquity, as well as perhaps to some extent its laziness.

Puw’s opera Y Tŵr (The Tower) is based by its librettist Gwyneth Glyn on a 1978 play by Gwenlyn Parry about the progress through life of two people, initially a Girl and a Lad (they are never named), then mature Man and Woman, and finally Old Man and Old Woman – seven ages reduced to three, or maybe more, since there is some progress (if that’s the right word) at each stage. It’s a grim journey in any case, watched over by the tower in which the couple seem to live and up which they proceed, age by age, until – in the libretto, though not quite so clearly in Michael McCarthy’s production – the Old Man, having been fed an overdose by his wife, disappears up the final ladder into – what? Heaven? Oblivion? You take your pick, but the disagreeable solution is the more likely to be the right one.

There is the Welsh lullaby, 'Suo gân', sweet then sourAny full-length two-person show runs the risk of monotony, and I must admit I wearied of this couple some time before the end, brilliantly though they were played and sung by Caryl Hughes and Gwion Thomas. But at no point did I tire of Puw’s score in this his first opera, a work of real imaginative power, full of movement and colour, and rich in ideas that responded to and intensified the drama. This is a chamber opera, with an orchestra of a dozen or so; but Puw found in this small mixed ensemble an amazing variety of sonority, and a flow of striking musical imagery that at times had one on the edge of one’s seat waiting for more.

As a drama, Y Tŵr is somewhat stereotyped and predictable. But Puw makes a virtue of this with musical reprises at each stage: there is train music (shades of Steve Reich) and butterfly music for the girl’s recurrent dream which, in the later scenes, turns increasingy nasty; and there is the Welsh lullaby, “Suo gân,” sweet in the first scene, soured by the third.

Not many composers have this much feel for the balance of moods and the ability to move easily between them (as Wagner said, opera is the art of transition). My only reservation would be that, like many first operas, Y Tŵr is a trifle overscored, a little too active in the orchestra. But Puw writes fluently for the voices, who seemed to ride above the web of sound without too much strain; and, as we already know, Welsh is a lovely language to sing, even if you’ve no idea what it means.

McCarthy’s staging is clear and unmannered, a single functional set (Samal Blak) with a bit of furniture moving and a symbolic rolling up of carpets to indicate a change of level. Mystery, though, is in short supply; the tower is nothing but the ladder, and the prosaic lives of these two characters (pictured above as Lad and Girl) – their loving and rowing and dreaming – are straight soap opera, largely devoid of poetry or spirituality. Maybe they deserve whatever revenge the tower has in store for them after all.

I wouldn’t be quite so hard on the MTW Ensemble, but they were certainly not at their best on this first night. Richard Baker conducted with plenty of oomph, but the ensemble was less than immaculate and tuning, in exposed unisons, sometimes shaky. This will improve, and Y Tŵr should be seen, here or on tour. Good opera composers emphatically do not grow on trees, even in the land of song, and Puw promises to be one.

• One further performance of Y Tŵr at the Sherman tonight, 20 May, then on tour in Wales