The staging of Wagner’s Ring Cycle is a flagship operation for the Edinburgh International Festival. Siegfried is the third part of the cycle; next year will see the final part, Gotterdamerung, and in 2020 ,the Festival will hopefully stage all four together. Last year, Die Walkurie was the operatic highlight of the festival; indeed, for many perhaps the finest concert performance of Wagner they have ever seen. So hopes are high that Siegfried this year will live up to that standard, particularly with a very fine cast. It almost does, but not quite.

Really, this is a borrowed concert performance of Siegfried as Mark Elder and the Halle Orchestra staged it in Manchester in June with some of the same cast. Elder is a great Wagnerian and the Halle are clearly very familiar with the music, and of course his direction, and this shows in a superb musical account of the opera, with luxury casting of the instruments, including six harps for some very limited parts of the score. It is very much a musical triumph.

Staging concert performances is a difficult business. You want the singers to convey the meaning by acting as well as singing. If done well, as in Die Walkurie last year, it can be more convincing than a clunky fully staged performance of Wagner’s rather difficult operas with dragons and horses. However, it does depend on the singers being fully committed dramatically as well as vocally and here is the main flaw of this performance.

Simon O’Neill is a very fine established Wagnerian. Indeed, his Siegmund in last year’s Walkurie was widely praised. Not only did he he sing the role well, he acted it well. His duet with Amber Wagner brought the house down at the end of the first act last year. However, he has just taken up the role of Siegfried and sings to a score (on an iPad) as he did in Manchester. Clearly, he isn’t secure enough in the part to range freely across the stage as other singers do.

This inevitably limits his dramatic impact, in particular during the final love scene with Brunnhilde when he appears more intent on his iPad than on his lover! Only when his singing finishes does he leave the safety of his iPad and give Brunnhilde a passionate kiss. Vocally, he has a good clean line, but when pushed the voice becomes metallic and hard. He doesn’t quite convince in this very difficult role.

The other singers on stage are of a very high standard. The first act is dominated by a superb performance of Mime by Gerhard Siegel, who not only sings, but acts superbly. Wotan The Wanderer is sung by the very fine Scot Iain Paterson, who compares very well to Bryn Terfel from last year’s Die Walkurie. Alberich is superbly sung and acted by Samuel Youn, a great young South Korean singer; Erda is beautifully sung by Anna Larsson and the Woodbird delightfully sung by young Greek soprano Danae Kontora who is a late substitution. Finally, Christine Goerke, the great American soprano is a wonderful Brunnhilde, although somewhat in isolation from Siegfried attached to his iPad.

Tonight’s is a great but flawed performance that may still be the operatic highlight of this year’s Festival.