Maestro, 2023, directed by Bradley Cooper, is in cinemas now and available on Netflix from 20 December.

There is a video of Leonard Bernstein rehearsing Gustav Mahler’s Das Lied von der Erde from 1974 with the Israel Philharmonic. The fourth movement, ‘Von der Schönheit’, is taken by Bernstein at a manic lick – so much so that an exasperated Christa Ludwig, the great mezzo-soprano, cannot keep up. ‘This is so much slower than we normally do it!’, exclaims Bernstein in amazement. After a brief unhelpful confab – ‘no one can hear the words anyway’, he limply reassures – Bernstein declares to the orchestra that this particular section is ‘always impossible’.

Bernstein loved the impossible. It gave his music-making an electrifying character. Achieving it must have driven his colleagues mad; witness his skirmishes with a gung-ho BBC Symphony Orchestra which bristles at the breakneck speed of his Enigma Variations, or a frankly lunatic attempt to direct Ravel’s fiendish piano concerto himself from the keyboard. After the cascades of wrong notes and panicked woodwind solos, the ovation is nonetheless enormous. His finest recordings – live and studio – still crackle with reckless, daring swagger and eye-widening candour.

Bradley Cooper’s Maestro, a passion project in which he both stars and directs, explores the various impossibilities entailed in being Lenny. There is the antagonism between his ambitions as composer and conductor, his efforts in the former tinged with frustration and regret, representing in turn a scar-like division in himself. There is his inability to reconcile his bisexuality with either social or domestic spheres, despite an uneasy truce with wife Felicia Montealegra, given a barnstorming performance by Carey Mulligan.

Such contradictions are set out in Matthew Libatique’s Janus-faced cinematography. Bernstein’s younger years – his big break at Carnegie Hall, the creation of hit ballet On the Town with Jerome Robbins, his burgeoning love affair with Felicia – are cast in black-and-white, with a boxy aspect ratio. His later years, entailing an ecstatic performance of Mahler’s second symphony at Ely Cathedral, the pressure on his marriage from his numerous affairs with younger men, and Felicia’s unsparingly handled decline and death from cancer, are cast in wide-angle technicolour, with sustained close ups giving the audience ample opportunity to scrutinise the (somewhat controversial) prosthetics that transformed Cooper into Bernstein.

Earlier sequences borrow from the mobile, gymnastic camerawork of West Side Story and revel in a dreamlike blurring of the boundaries between art and life. When Bernstein gets the call to conduct the New York Philharmonic for an indisposed Bruno Walter, he bursts from his bedroom after a percussive slap on the bottom of his male lover onto the balcony of Carnegie Hall itself, accompanied by music from his 1954 score to On the Waterfront. Later, with Felicia, the ballet On the Town – the story of three sailors out on the razz – dramatises their own whirlwind romance, with Lenny’s face superimposed. In one respect it recalls the way that for Bernstein life and art really were indivisible – his shamanic music-making sees him merge wholly with score and composer. ‘I love music so much’, Bernstein says, ‘it keeps me glued to life.’

The other implication is that it’s Lenny’s world and the rest of us are just passing through. That turns out to be both adventure and curse for those close to him, as his sister Shirley (Sarah Silverman) points out. It is especially so for Matt Bomer’s David Oppenheim, Bernstein’s clarinettist lover, whose quiet sadness when Lenny falls head-over-heels for Felicia is exquisitely understated; later in the film, they walk together past Central Park and silently imagine what kind of life they could’ve led together.

The use of silence in the film – made all the more intense by the long, lingering wide shots that Cooper favours – is one of its most powerful features, and clears plenty of space for Cooper’s uncanny imitation of Bernstein’s gravelly, nasal tones. The fact the soundtrack – with the exceptions of Mahler and a little Beethoven – comes exclusively from Bernstein’s own compositions, redoubles the feeling that his consciousness is the movie’s centripetal, irresistible force.

Mulligan’s Felicia is the one who disturbs this momentum; it is through her that the price of being in Lenny’s orbit is totted up. In one scene, the couple fight in their New York apartment as the Thanksgiving Day parade rolls past; after a withering comment, Felicia leaves Bernstein dumbfounded, standing pitifully slack. In the silent aftermath, a giant inflatable Snoopy float hoves into view through the window – turns out Bugs Bunny wasn’t the only cartoon conductor after all. What looks majestic and romantic in one light might be garish and bloated with hot air in another. Equally, as Felicia’s illness worsens, we see the nurturing, loving Bernstein who made such an engaging teacher and broadcaster. This tender manifestation of his extroversion is offset in the film by another kind: coarse, sloppy, selfish, as Bernstein increasingly turns to booze and drugs.

That public and private blur for someone who goes through the emotional wringer night after night on the rostrum is given striking staging at the film’s outset. We approach Bernstein from behind, as he is seated at the piano playing the glassy, bittersweet postlude from his 1983 opera A Quiet Place. But as the camera pans we see his sensitive introspection is being filmed for an interview. The implication perhaps is not that Bernstein is faking it – in no way does the film suggest he is a manipulator or a con artist, even if a later scene of him canoodling with one of his Tanglewood Summer School conducting students hints at something rather more unseemly. Rather, his most intimate emotional experiences are up for public consumption, exacerbated by a desperate need for, and love of, being around other people.

Felicia sees great pain and anger in Bernstein, which his music-making both channels and tries to expurgate. This reaches its cathartic zenith in his performance of Mahler in Ely Cathedral, crowning the second act of the film. Cooper’s mannerisms, for anyone familiar with the original film of the concert, are meticulously observed; the orchestral and choral contributions from London Symphony Orchestra and their chorus, searing. As the Cathedral erupts after the final note, Bernstein walks into the wings to embrace Felicia, who holds him tight – more like a mother than a lover – and reassures him that there will be no more pain and hate. It is a fabulous use of the music, coordinating its purifying, cleansing power with Cooper’s own narrative arc, and pivoting from huge spectacle to private moment with remarkable agility.

Curiously, one of the film’s disappointments is in fact the recordings created for the soundtrack by the London Symphony Orchestra and Yannick Nézet-Séguin, conductor of the Philadelphia Orchestra and Met Opera who painstakingly prepared Cooper for his miraculous acts of physical mimicry on the podium. The sound is prissy and over-engineered, lacking the acidic vigour and recklessness of Bernstein’s own recordings of Candide or On the Waterfront; it sounds like it’s never even tried a cigarette, let alone smoked a whole pack (unlike the perpetually smouldering maestro).

‘Summer still sings in me’, Bernstein says at the end of the film. Cooper’s performance is wholly convincing, not least because his face is as animated and expressive as Bernstein’s (exemplified by the way he could conduct the Vienna Philharmonic with his eyebrows alone). The film is a vivid study of a complex couple, one of whom is dangerously alive and perhaps suffocatingly selfish. But a consequence of this is that we never really explore the tension between Bernstein’s life as conductor and composer, set up at the beginning. Indeed, we seldom see Bernstein composing.

In another respect, the movie seems unsure as to how reverential it wants to be about the Maestro (a term that is only really served in UK musical culture drenched in sarcasm), or whether it wants to be more cautious and standoffish about this charismatic and problematic figure. The film could do more to examine the aura of greatness that remains mostly intact around Bernstein; a recent Guardian article interviewing former LSO players recalls the incredible affection many players felt for him, but also unwanted advances and sad, petty cruelties. The film quotes Bernstein at the outset: the function of a work of art is to provoke questions. Cooper could dare to be more ambivalent, given the richness of his subject.