Guildhall School of Music and Drama at The Pit, Barbican

Neither straight play nor musical recital, an event as idiosyncratic as this dramatised biography of Ivor Gurney (1890-1937) could easily elude categorisation and pass by unreviewed. That would be a shame, so here it sits, faute de mieux, in the pages of Whatsonstage/Opera. Not quite right, but near enough.

The Gloucester composer-poet's existence was a long, slow descent into tragedy. Outwardly a country bumpkin ("Blister my kidneys!" as he might say), his work was described by his biographer, Michael Hurd, as "flawed, but undeniably individual and certainly touched with genius". As with art, so with his life, as the actor Richard Goulding brilliantly shows in his forensic portrayal of Gurney's progression from assistant organist at Gloucester Cathedral through study at the Royal College of Music to trench warfare at the Somme (Gurney was invalided out after being gassed). His subsequent twenty-year decline into insanity is enacted by Goulding with unflinching engagement and honesty.

Iain Burnside is best known as a pianist, but in A Soldier and a Maker he shows himself to be a playwright of surprising technical skill – except, perhaps, in the matter of choosing snappy titles. With its varied pace, confident line of action and recourse to comic interludes, Burnside's vivid narrative has a freedom that transcends the normal confines of verbatim theatre. It is extraordinarily moving.

Designers Giuseppe and Emma Belli frame the stage with a photographic silvan vista that appears to represent Gurney's yin and yang, At first we see A E Housman's 'loveliest of trees'; look more closely and we also perceive something darker in the "naked and stiff branches of oak, elm thorn" (‘Last Hours' by John Freeman). On either side of the stage sits a piano – and that's it. Occasional props come and go; naked 30-watt light-bulbs flicker. (Now where can you get one of those nowadays?)

The pianos are deftly played by several performers, all of them (except Goulding, who is an alumnus) current students at Guildhall School of Music and Drama. Gavin Roberts and Justin Snyder shoulder the main burden while playing only incidental roles within the action. Among the large supporting company some of the acting is barely functional, although there is a terrifically nuanced contribution from Bethan Langford, hrartbreaking as Gurney's loyal sister. Elsewhere, some of the most eye- (and ear-)catching work comes in blink-and-you'll-miss-'em performances: Catherine Reynolds's compassionate nurse, for example, and Timothy Connor's rich, Terfel-esque bass of a soldier.

The singing is, of course, the Guildhall students' trump card, and there is plenty of it. All the best-known songs are present and correct, some presented as written, others in discreet arrangements, presumably by Burnside himself, such as Gurney's setting of F W Harvey's ‘In Flanders' which  achieves a devastating impact when assigned to a quartet of Great War combatants.

The playwright's self-directed production is as buoyant as his script but, as with his subject, it is not without flaws. Victoria Newlyn's dancy movement work threatens to tip the mood into bathos at key moments, although thankfully it never lasts long. Elsewhere, Burnside's refreshing attention to period detail (costume, haircuts) is let down by the recurring anachronism of a modern, anti-red-eye camera flash. These, though, are incidental concerns in a production that sweeps the audience towards the terrible desolation of its conclusion, a sadness rendered all the more poignant by the two-hour musical celebration that precedes it.

- Mark Valencia