SO here we are, officially, in the summer, winter tents packed away, some orchestras out on the road with summer stuff for a wee bit, others already with their eye on chunky festival appearances from Fife to Edinburgh and London.

The Perth and Orkney festivals have been and gone. But the fabled "quiet summer period", about which I was regaled years ago in my early days on The Herald, is a bit of a fiction. If there is such a thing it's probably somewhere, briefly, in July. The sun has blazed, and disappeared, in the course of the last two sentences. And that, without too much of an exaggeration, feels just about the length of the "summer lull".

Still, this precise period is one of my favourite slots in the musical calendar. Why? Because this is the time of the year (one of two) when the best of Scotland's young musicians take centre stage, let us hear the results of their hard work and show us the sharp edge of their talent. The classical limbs of this small army will have their reactions honed, their skills mobilised and disciplined into a collaborative and corporate effort, then unleashed on classical music's top-drawer repertoire in a series of public concerts in which not one concession is made to age or ability. They are the best of the best, and that, precisely, is what is expected of them. It's always a thrill to take your expectations into the concert hall and hear these youngsters released on demanding repertoire, playing with the hunger and absence of complacency that you would expect from the most seasoned and mature professionals.

These are the National Youth Orchestras of Scotland (NYOS) and they are all coming out to play. There are three of them, graded in ages, with, of course, technical and musical ability taken into

account. It's not a game or an out-of-school summer musical activity. It's a skilled, disciplined, corporate endeavour. Every youngster joins via a rigorous audition. Successful applicants are organised into the three orchestras, the NYOS Junior Orchestra (8-12) the NYOS Senior Orchestra (13-18 years old) and the full-sized, full-scale symphony orchestra, the National Youth Orchestra of Scotland - "big NYOS" in common parlance- at 18 and upwards, towards mid-twenties.

A total of 298 youngsters have been selected for the three orchestras, 101 in the juniors, 85 in the seniors and 112 in "big NYOS", the flagship orchestra of the oldest students. Each orchestra will be sent in turn for an intensive, five-day residential course in Strathallan School in Perthshire, beginning next Tuesday with the NYOS Juniors. They will be coached by a team of 15 professional musicians assigned to each orchestra, who will be among Scotland's most seasoned pros from the national orchestras and freelance community. There is also an appointed team of pastoral staff who will be in charge of the complex business of "normal life" away from home, and the intricacies of young people living and working in a concentrated environment.

Each of the three orchestras will have its own conductor who is responsible for his or her orchestra, which they must bring up to the highest possible standard, with all the polish, refinement and expertise that can be attained within five days. There can be no passengers. Personally, my view is that, in both individual and group endeavour, it is among the most formidable challenges young musicians can face. No prisoners can be taken: it's too serious; too close to the big-time; and people are going to pay to hear it. It has to be good. You'll gather that I don't take a watered-down or compromised view of this particular musical activity, which provides a unique barometer for gauging just how far Scotland's best youngsters can go. Go and hear them. It's the only way you can know.

All concert details are on the website. The Juniors are off first, with conductor Holly Mathieson and music by Gliere, Maxwell Geddes and MacCunn in Greyfriars Kirk next Saturday (11th) at 6pm; James Lowe takes the Seniors on Thursday 16th at 7pm (watch the different times of these) in Glasgow's City Hall with a programme that concludes with Sibelius' mighty First Symphony.

Then, ultimately, it's the full Symphony Orchestra with conductor Rory Macdonald and stellar pianist Danny Driver, who are off on a major international tour to China where, with three concert dates in Shanghai Grand Theatre (August 1) Beijing Concert Hall) (August 5) and Tianjin Grand Theatre (August 6) they'll play a blockbuster programme of Shostakovich's Festival Overture, Erik Chisholm's First Piano Concerto, Piobeaireachd, and Rachmaninov's Second Symphony. That concert will receive a single Scottish performance on the eve of the tour, in Perth Concert Hall on Wednesday July 29, 7.30pm. Quite a summer for NYOS.