When Polish company Song of the Goat were last in Edinburgh, they tackled the cultural behemoth of Shakespeare’s King Lear. Now they lend their unique choral interpretation to a no less ambitious subject: Scottish tradition.

Return to the Voice is inspired by the nation’s ancient music, transforming it into a piece that uses little more than the extraordinary vocal instruments of the company. It’s more concert than theatre, but on the Fringe such distinctions become increasingly irrelevant. Return to the Voice is, in its powerful interplay of voices, deeply theatrical. It is just drama for the ears instead of the eyes.

The choir of twelve singers, six men and six women, bathe St Giles Cathedral in song – if, indeed, song is the right word. The performers do not sing so much as sculpt the air with their voices. The contours carved by their carefully controlled sound curve in all directions, before exquisitely converging to hang in the still air of the cathedral.

This is music that seems to vibrate from the very stones that surround it, music that feels as ancient as the stained glass windows through which the evening light wanly trickles. It’s the sound of Scotland, triple distilled and filtered through Song of the Goat’s own distinct style. The structure of the evening frames this perfectly, opening with a guest performance from musicians reciting original Gaelic songs to establish the genealogy that Song of the Goat are drawing from.

The venue is also inspired, imbuing proceedings with a heady hint of the spiritual. Acoustically, St Giles Cathedral is a dream, while its architecture carries evocative traces of the history to which Song of the Goat gesture. And gradually, by some powerful alchemy of sound and space, a little bit of the show creeps its way under the skin, reluctant to release its grip.