The core requirements are unchanged. Musicians need orchestras for their livelihoods in the city. It may not be much of a living. Many in London earn less than £30,000 a year, some are reduced to driving cabs. Yet they persist with an arduous vocation because it is what they enjoy, what they believe in and what they were trained for in state education (whether we are maintaining too many music colleges is an argument that has wittered on in government for nigh on 30 years).

In Belfast, Birmingham, Bournemouth, Cardiff, Glasgow, Leeds, Liverpool, Manchester and Newcastle, musicians earn rather less than £30,000 but a couple who both play in an orchestra can raise a family quite comfortably on a double salary and will obtain a higher quality of life than they could in the Big Smoke. They also enjoy higher social status and recognition, as well as richer possibilities of private tuition and playing chamber music. All in all, it's not a bad life and the bonus of local pride puts a spring in the step of regional musicians that I seldom encounter in capitals. When Liverpool goes on tour, it takes along a charabanc of supporters.

The value of an orchestra to a city is a matter of pride and self-worth. If Philadelphia were to lose its sound, the metropolis risks fading to blank. Whether that threat is enough to winkle extra millions from its richest citizens remains to be seen.

Beyond civic self-interest lies the potential for social cohesion. What the twinkle-eyed chorus master Gareth Malone has shown in several television series is that music has the capacity to change the lives of those who feel abandoned by every other social organisation. Starting from an East End community project at LSO St Luke's, the orchestra's music education centre, Malone has rallied people of all ages in sink estates, youth clubs and army barracks to come together and find themselves in a musical activity. It is an initiative that could not have flourished without the bedrock of an orchestra to give it life. The LSO has led the way in offering its players opportunities outside the concert hall — in hospital visits, prison rehab work, small ensembles and remedial teaching. The players have richer working lives than ever before and the city benefits enormously.

Simon Rattle's projects with immigrant communities in unified Berlin have had similar resonance. Dudamel in Los Angeles is a symbol of social inclusion in a deeply schismatic city. An orchestra in the 21st century is more than the sum of its parts, more than the ear beholds. It is woven deep into the social fabric, so deep that its abolition becomes almost impossible.

Louisville, as I write, is emerging from bankruptcy protection. Syracuse, which I visited in deep doldrums last winter, is trying to form a new part-time orchestra. The sacked musicians of Rio have regrouped as an independent ensemble. You can shut a theatre but you cannot keep a good orchestra down. There will always be an audience for what it has to offer.

And why is that? Because in a lifestyle of wall-to-wall wi-fi and instant tweets, the concert hall is one of the few places where we become reachable, where we can switch off our lifelines and surrender to a form that will not let us go for an hour or more. The symphony orchestra is our relief from the communicative addiction. It forces us, willy-nilly, to resist the responsive urge. It is a cold-turkey cure for our reactive insanity, our self-destroying restlessness.