At the height of his career, Czech-born composer Josef Mysliveček was the most prolific and sought-after figure in Italian opera, bound for immortal celebrity. Nearly three centuries later, his name isn’t forgotten to classical music scholars, but neither does it have anything approaching household status; the facts and records of his personal life, meanwhile, have largely been lost to history. Via a blend of free narrative speculation and exacting musical presentation, Petr Vaclav’s stately, sumptuous biopic “Il Boemo” seeks to restore a degree of iconic status to a talent latterly overshadowed by relative 18th-century contemporaries, albeit not with much swagger or modernity of its own: This is costume drama of a traditional, ornately brocaded stripe, a classical music lesson for classicists.

That’s not likely to do “Il Boemo” any harm as it further travels the festival circuit following its world premiere in San Sebastian’s main competition, the film’s profile enhanced by its selection as the Czech Republic’s candidate for the international feature Oscar. Older arthouse audiences, in particular, should turn out for a lush, multilingual European co-production in the tradition of Gérard Corbiau’s ‘90s success “Farinelli: Il Castrato” — or, more optimistically, Milos Forman’s “Amadeus,” which, like “Il Boemo,” told the tale of an associated career ultimately consumed by the prodigious legend of Wolfgang Amadeus Mozart. 

As Mysliveček — known in Italy as Il Boemo (The Bohemian) to admirers unwilling to grapple with the syllables of his last name — Vaclav has cast charismatic sometime pop singer Vojtěch Dyk, a selection that cannily suggests the composer’s magnetism in his pomp, even if the film’s contemporary allusions are otherwise scarce. Working from a patchy confirmed biography, one heavily dependent on correspondence with Mozart in the Czech composer’s final decade, Vaclav’s episodic script fashions him here as a cosmopolitan playboy interloper in Italian high society — at least, after a brief, Rome-set prologue that introduces our hero shortly before his impoverished death in 1781, aged just 44, his face masked to conceal the ravages of syphilis.

As we rewind to brighter days in 1765, DP Diego Romero — best known for his collaborations with docmaker Roberto Minervini, here working in an altogether more opulent register — practically flushes the frame with Venetian gold. Unmasked and unmarked, the young Czech migrant climbs the Floating City’s social ladder by offering music lessons (and much else besides) to well-to-do womenfolk, breaking the heart of one aspiring cellist as he vaults into an affair with older aristocrat Rezzi (Elena Radonicich). Eventually he secures the ear of volatile star soprano Caterina Gabrielli (an imperious Barbara Ronchi), whose hard-won admiration is key to his ascendance in Italy’s thriving opera scene — itself presented in a transitional state between Baroque grandiloquence and Classical lightness.

Mysliveček adapts nimbly to changing times and tastes, wowing such lofty listeners as the callow young King of Naples, yet is plagued by the sense that his artistry is never reaching or resonating as far as it could. That perception is echoed by the most constant and elusive of his many lovers, unhappily married noblewoman Anna (Lana Vlady), who advises him that his music “could be felt more deeply.” That’s a blow to the ego, certainly, though perhaps not quite as dispiriting as his burgeoning acquaintance with the teenaged Mozart (a deliciously bratty Philip Amadeus Hahn, himself a young piano prodigy), who, in the film’s wittiest scene, magnificently riffs on one of Mysliveček’s compositions with a crushing lack of visible effort.

Not that “Il Boemo” treats the Czech composer’s work with similarly offhand disdain. For newcomers to his oeuvre especially, its glorious musical treatment here — conducted by Václav Luks and played by his renowned Baroque orchestra Collegium 1704 — is the film’s overriding pleasure, delighting even when the storytelling occasionally palls across a deliberate 143-minute runtime. Yet for all Vaclav’s dedication to his subject (whom he previously explored in his 2015 documentary “Confession of the Vanished”), Mysliveček doesn’t quite emerge as a whole character: Only a single, tone-shifting scene in the composer’s native Prague (with Dyk additionally playing his twin brother) alludes to an otherwise vaguely drawn past.

The film’s Italian milieu, on the other hand, couldn’t be more vividly illustrated, fusing rich historical locations with grandiose design work by Irena Hradecká and Luca Servino. Andrea Cavalletto’s costume design, meanwhile, does more than just throw embellished splendour at the screen, instead thoughtfully recycling items to remind viewers how Mysliveček, even at his peak, was never too far from seamy ruin: In particular, one gorgeous frockcoat in turquoise velvet follows him through the years, a dandy’s aspirational uniform at one point, a literal marker of faded glory later on.