Trembling, gasping and semi-naked, a middle-aged man stands agape in a spotlight, his only protection against the terrifying darkness before him the gleaming French horn he clutches in his sweaty hands. This solo show is both the poignant tale of how that recalcitrant instrument brought its owner a sort of salvation, and a celebration of the joyous, life-affirming power of music.

Based on the book by the arts journalist Jasper Rees and adapted for the stage by the author and by Jonathan Guy Lewis, who performs the piece, the play unfussily and unpretentiously encapsulates something of the indefinable elation that art can bring to the human existence. It is also very funny. With his marriage over and his days assuming a grey predictability, Rees, poking through the debris of his past - ancient school reports, wedding photos - unearths the horn he failed to master as a child. Fluctuating between quixotic hope and wry pessimism, he sets himself an awesome challenge: to play Mozart’s Horn Concerto No 3, K447, in a concert for the British Horn Society.

In Harry Burton’s engaging production, Rees’s quest to achieve anything approaching competence on this most treacherous of wind instruments leads to encounters with some intriguing characters, among them the intimidatingly intense German virtuoso Herman Baumann and the compassionate Northern horn-player Dave Lee, who becomes Rees’s mentor. He imagines the jocose relationship between Mozart and Joseph Leutgeb, the Viennese cheesemonger for whom he is believed to have written K447; and muses on the fate of the horn player Dennis Brain, killed in a car crash.

The process also leads to the reawakening of memories. Rees revisits his moments in the school orchestra, when he was distracted from the confounding tadpoles on the musical stave by a young Lady Diana lookalike with “an unbelievably big violin between her legs”. He recalls his sense of inadequacy, and his public humiliation, as he struggled and failed to make music out of breath, spit and 16 feet of coiled brass tubing. With the date of his concert performance speeding towards him, will he face failure once again?

Well, there’s no sentimental climax here. Instead we are treated to a rendition of the Mozart by Lewis that swells and soars with feeling. It’s a fitting finale, a brassy burst of celebratory sound in honour of the imperfect and exhilarating business of being alive.

Box office: 020-7240 6283

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010