As it whirs into life, a voice sings out, raw and untutored, backed only by a sparsely picked guitar and highlighted by a distinctive yodel.

This, as Duncan McLean’s Lone Star Swing Band tell us over the next 90 minutes, is the voice of Thomas Fraser, not some undiscovered Nashville pioneer, but a Shetland fisherman from Burra who died in 1978, leaving behind a box-full of at least 1000 home recordings.

In this low-key dramatised concert, McLean and co relate how a shy island boy became smitten by music while bedridden for two years with polio and only the radio for company. The guitar Fraser taught himself to play allowed him to interpret the work of Jimmy Rodgers, Hank Williams and The Inkspots. A life of quiet hardship led to Fraser’s untimely death in 1978 aged just 50.

Beyond their own exemplary playing, McLean, lap steel player Dick Levens, fiddler Fiona Driver, drummer Iain Simpson and bassist Iain Tait frame his story in snapshots of their own musical history in Vicky Featherstone’s homespun National Theatre of Scotland production. When they become Fraser’s virtual backing group on his spartan reading of Over The Rainbow, played through the reel to reel, it’s as if Fraser is in the next room, too bashful to take the spotlight.

Star rating: ****