Imagine a parallel universe where the greatest democracy on earth had thought better than to legislate against a fifth of its own people because of their skin colour. Living in Utopia might have allowed Scott Joplin to transcend his typecasting as ‘The Ragtime King’; and just perhaps his 1911 opera Treemonisha might have been cut the understanding and respect it clearly deserves; and just perhaps a new recording would have been unnecessary.

Too many ‘mights’ and ‘perhapses’, I know, but conductor Rick Benjamin’s extraordinary booklet essay about his reconstruction of Treemonisha tells us how Joplin lived his whole life based on little more than a wing and a prayer. This set is the culmination of two decades of research, social anthropology and painstaking forensic reconstruction. And I can’t think of a more worthwhile task – musical archaeology that needed doing – than rescuing Joplin’s sole surviving opera from obscurity and misunderstandings, some well-meaning, others inexplicably stupid and sloppy. Understanding Treemonisha is not just about hearing Joplin’s achievements in the round; it’s about gaining a proper understanding of black culture during that historically nebulous period when jazz was in its baroque infancy.

Benjamin packs nearly 70 pages of densely spaced text (illustrated with evocative sepia photographs, newspaper clips and other period memorabilia) with Treemonisha’s painfully convoluted and troubled history: the frustrations, the productions that never happened, the legal wrangles following Joplin’s death that led to – and you’re not going to believe this – all the original performance materials being casually dumped in the trash can in 1962. Joplin’s purpose was, Benjamin thinks, ‘to blaze the trail for serious black artistry by providing a vehicle for black performers’.

After listening to Benjamin, the failings of Gunther Schuller’s 1975 DG recording become immediately obvious. Schuller’s glutinous orchestration is pitched somewhere between Falstaff and Oklahoma!, with some harmonies discreetly swung ‘jazzwards’ in a desperate attempt to clinch Treemonisha as a proto-Porgy and Bess. Benjamin’s orchestrations, modelled after a smattering of surviving Joplin orchestrations and period orchestral primers, were made for his own 12-piece Paragon Ragtime Orchestra: one instrument to a part, cornets instead of trumpets, authentic antique percussion instruments.

Using cornets in place of trumpets might seem trifling but the subliminal impact of all Benjamin’s attention to various tiny details makes this Treemonisha feel instinctively right. Next to Porgy and Bess, Joplin’s plot – a plantation couple dream about having a child who might teach their community to aspire to better than superstition, and bingo, they find a newborn baby under a tree – is intimate and small-scale. The couple, Zodzetrick and Monisha, express themselves in rootsy, soulful language; clearly Treemonisha was never about the vainglorious spectacle of European ‘grand’ opera. Benjamin’s light-on-its-feet orchestration fits the music: genteel melodic lines swim like fish through pure water.

Voices carry now too, rather than bob along the spray of Schuller’s orchestral tempest. Edward Pleasant and AnnMarie Sandy (Zodzetrick and Monisha) banish operatic pomp; Anita Johnson’s Treemonisha is sincerely felt. The star of the show, though, remains Joplin. For a composer expert in ‘closed form’ – harmonic ambiguity overrode ragtime’s rigid 16-bar phrases to flat-pack the structure into itself – the wonder of Treemonisha is Joplin’s flair for dramatic trajectory, the intensity of thematic development making his writing spring eternal. This is the most important document about the history of American composed music to have appeared in a long, long time.