It wouldn’t quite do to overpraise the National Youth Orchestra of Scotland. For many people, the word “youth” is enough to lower their expectations. They imagine they’re in for such a cacophonous evening of split horn notes and scratchy strings that when the orchestra turns out to play half decently, the tendency is to bestow the most extravagant of plaudits, as though the NYOS is about to knock the Berlin Philharmonic off its perch.

It isn’t. The orchestra is clearly well disciplined, even if there is something of a military mentality in the way they tune up in sections and stand to face the audience as though on a parade ground. The sound is warm but slightly hazy around the edges, as though seen through a soft-focus lens. The steady upward tramp of tutti strings in Wagner’s Prelude to Die Meister-singer was impressive for its coherence, but lacked the sense of slightly breathless impulse that can make this such an exciting piece of music - the possibilities of individual expression had been subjugated by the importance of playing in time.

This was the last date in the NYOS summer tour, a series of five concerts from Birmingham to Aberdeen, the culmination of a summer course which welds 116 young musicians from the age of 12 to 21 into a single orchestral body. Some players are long-standing members but essentially the NYOS is transient, freshly moulded each year.

The Glasgow Royal Concert Hall was barely full, but even so this year has been special. The orchestra’s 21st anniversary was celebrated with appearances at Holyrood House and at the wedding of the orchestra’s patron, Prince Edward. A CD is in production of repertoire taken from this and previous summer tours.

After the Wagner, the ebullient violinist Tasmin Little joined the orchestra for what was in many ways a rather extraordinary account of the Tchaikovsky violin concerto. The first movement was markedly slow. Little appeared to relish the conversational pace and picked out the decorations with pointillist clarity. She interposed herself between the conductor, Takuo Yuasa, and orchestra, giving huge encouraging smiles to whichever section happened to be playing, and effectively regulating the pace by the simple expedient of playing so clearly that it was impossible not to follow her. Who was really in charge? The pace picked up in the finale but with it came the first signs of ragged playing from the orchestra.

The concert ended with both suites from Ravel’s Daphnis and Chloe, requiring a huge range of orchestral virtuosity and colour. It sagged here and there but the key moments - for example the magical sunrise in Lever du jour and the great closing bacchanal - were brilliantly executed.