What is it about the string quartet? Why is a form that is so intimately linked to the history of music, so tied to the greats of the past, still so popular with composers today? The symphony is now a rare beast, even the concerto is often written almost apologetically, and yet the string quartet – which for the general public may represent almost the quintessence of classical form – seems to go from strength to strength.

I’ve wondered about this before, but the question came back to me the other night after hearing a performance of Jörg Widmann’s Fourth Quartet (out of five), but also having seen that James Dillon’s Eighth had just been premiered, as had Rebecca Saunders’ “Unbreathed” to great acclaim. Nor do you have to look far to find other examples: the ten quartets of Peter Maxwell Davies, Wolfgang Rihm’s thirteen and counting (I’m writing this listening to his Third Quartet), and it doesn’t make much difference what particular style or aesthetic the composer comes from, Philip Glass and Brian Ferneyhough don’t have much in common except for fine string quartets.

Part of the answer must lie in practicalities, in cost and economy. A string quartet is more likely to be played than something written for a hundred-strong symphony orchestra; it’s more easily transportable, more easily fitted in to a regular concert programme (the Widmann I heard was sandwiched between Haydn and Tchaikovsky). Another reason surely is the commitment to new music by many quartets, especially younger quartets who have followed the example set by the indefatigable Ardittis (the Kronos having in my view taken the wrong path with their move into world music): Quatour Diotima, Minguet Quartett, and the Heath Quartet are just the first names to come to mind.

But there must be more to it than that. Perhaps it’s linked to another question: Why the string quartet and not the string trio? The trio is too simple and the difference that the second violin makes is remarkable, leading to the perfect combination and balance allowing for complexity and clarity, add a second viola or cello and the balance is lost again.

Unless of course your name is Mozart or Schubert.