EXCERPT Essays as I once knew them were always meant to consist of a certain number of words. There were rules—ways of making an argument, of finding sources and quotations to back it up, of introducing and concluding—that seemed at first frustratingly impenetrable, like the secret code of some exclusive club. I doubted I’d ever work it out, and decided that if I ever did, and if I one day came to teach others, I would help them decipher the code. ‘The essay’ that many of us know if we’ve studied in formal educational settings — a piece of writing that should consist of a certain number of words and have a certain structure — is a very specific form that derived from a more indefinite sense of what an essay could be. The meaning of the word has its origins in the old French word essai, meaning the ‘action or process of trying or testing’, as in Daniel Defoe’s use of the term in The Complete English Tradesman in 1725, where he advises that a man should not marry before he has ‘made an essay by which he knows what he can and cannot do’ in his trade and business. Or in painter Joshua Reynolds’s reference, in his Discourses to the Students of the Royal Academy in 1778, to ‘[a]n artist, in his first essay of imitating nature’. Another variant derives from assay, referring to the ‘trial imposed upon an object, in order to test its virtue, fitness, etc’, as in the obsolete sense of the ‘trial of metals’. We find this usage for example in the Philosophical Transactions of the Royal Society in 1668: ‘The Ore being ground […] they divide it in several heaps, and then by lesser Essays, they find out how much silver is contained in every heap.’ By the time we get to Charles Dickens, however, the far more restrictive definition has appeared, its formal constraints already the subject of Dickens’s ironic wit: in Our Mutual Friend (1865) Mrs Peecher ‘could write a little essay on any subject, exactly a slate long, beginning at the left-hand top of one side and ending at the right-hand bottom of the other, and the essay should be strictly according to rule.’ Over the course of about a hundred and fifty years, then, the term ‘essay’ ranged widely, encompassing a vast range of experimental possibilities that did not at all have to exist within the realm of writing, but it has come to refer most usually to something both written and tightly prescribed. Audio essays can return us to this broader sense of what essays can be and have been, to their potential for trying out new forms and mixtures and testing rules and boundaries.…