One of the delights of the Edinburgh Fringe is getting into venues you might pass by routinely all year and yet know nothing about. The Royal Over-Seas League in Princes Street was a case in point: it provided a charming boutique venue with a bar giving views of the Castle, Princes Street Gardens, and the street itself, busy with people at the start of this festival.

The Fringe programme billing for this early evening concert promised Scots songs from James Oswald, Haydn, Resphigi and James MacMillan, featuring mezzo-soprano Beth Mackay with Scottish players Paul Livingston on violin and Ian Watt on guitar. Apart from the Oswald, what we actually got was a completely different programme with soprano Ginny Wilson. Singers can get unwell and may be suddenly unable to sing: it comes with the territory, and audiences understand this. On this occasion, a completely different concert was offered with absolutely no explanation from anyone. It was particularly disappointing for those who came especially to hear the billed singer.

What should have been a concert featuring Beth Mackay became one that showcased young guitarist Ian Watt’s considerable talent. Scottish composer James Oswald (1710–69), who would eventually become chamber composer to King George III, published much Scottish traditional music and wrote Colin’s Kisses in the Baroque style. Watt provided perfect and positive accompaniment to Ginny Wilson’s clear soprano lines, lively and optimistic in the “Meeting Kiss”, and melancholic in the “Parting Kiss”. Paul Livingston interposed sensitive phrases on the violin between the verses.

Douze études pour guitare was commissioned by guitar virtuoso Andrés Segovia and written by Villa-Lobos when he was in Paris in 1929. Here, Watt played the final four études with lots of attention to detail, and plenty of variation in tone, from sweet-sounding notes near the fingerboard to harsher tones near the bridge. Even struggling with a bottom string which doggedly refused to stay in tune, this was a compelling and stylish bravura performance.

Watt was joined once more by Ginny Wilson for Siete canciones populares españolas by Manuel de Falla. The songs were written when de Falla was in Paris at the start of the war in 1914 before returning to Madrid, and Watt explained that arrangement of the original piano accompaniment for guitar was groundbreaking. It demonstrated that it was not possible to transcribe directly from one to the other as more work was required to achieve the desired effect. Wilson sang the seven short songs sweetly enough, where perhaps an earthier tone would have been more in keeping with the folky tradition, but Watt’s playing was mesmerising to watch, particularly in the extended use of harmonics.

It was finally Paul Livingston’s turn to shine in Paganini’s Centone di sonata in A minor, in a splendid duet with Watt, for Paganini was a guitarist as well as a violinist. In two movements, with flowing bel canto lines from the violin in the first and fun and games in the second as both players took consecutive passages together at wildly different and varying speeds. It was entertaining seeing them watch each other very carefully to see what way the next phrase would go.

Finally, Ginny Wilson joined both for a haunting arrangement of Gershwin’s “Summertime” from Porgy and Bess, and returned for an encore of the traditional Scottish song “Ye Banks and Braes”. Although this concert was a bit of a surprise, it was certainly enjoyable, and very much Ian Watt’s evening.