You could be forgiven for assuming that Damien Chazelle has a particular focus on making films about music. In fact, what his blistering debut Whiplash and La La Land actually have more closely in common is that they’re both about commitment and conviction. Which is mildly ironic, as there’s not a lot of that in evidence in the latter.

Is La La Land a musical or an homage to musicals with occasional musical numbers? Is it about following your dream, or about how dreams change? Is it a love story, or about two individuals making their own way? I’ve never felt more divided in opinion about a film before, and I trace this back to the divided soul of the film itself, and perhaps moreover down to the divided nature of its auteur: I love the work of Damien Chazelle the director, but when he takes his turn as a writer I struggle.

In fact, I had a similar problem with Whiplash, wherein I could only accept its polished, perfectly timed brilliance once I’d parked my opinion of its premise (that abuse is food for genius). In La La Land, jazz pianist Seb (Ryan Gosling) is a mildly more palatable talent, as he struggles to fulfil his dream of opening a club dedicated to what he believes is a dying form of music. On his journey, he blasts into the life of aspiring actress and writer Mia Dolan (Emma Stone), and their parallel dreams are at the heart of the rest of the story – as is the question of their ability to fulfil them.

At one point, it looks like Seb might be taking the story in an interesting direction; Chazelle circles back again to a previous theme in unpicking whether relationships are bad for creativity, and vice versa, when he introduces Keith (John Legend), who tempts Seb off the path and pays lip service to the idea that media don’t die so much as evolve. Mia attempts to steer things back on course, but at this point it’s hard to know whether that is or isn’t the right thing to do – the evolution of Seb’s dream seems to bring him more pleasure than the original plan ever did – although when Mia also suffers a setback to her plans Seb resolutely bullies her back into action. Is changing a dream an admission of defeat? Is it ‘growing up’? Is that maturity or losing one’s childlike joy? It’s impossible to tell in a tale that doesn’t so much leave things open-ended as, at times, directly contradict itself.

It’s also impossible not to raise one of La La Land‘s other great contradictions. Set in LA – intended, quite clearly, as a love letter to the city of stars – it boasts a massively, realistically diverse supporting cast, and some attention has clearly been paid to recognising the distinctly black roots of jazz as a musical movement. And yet the next step – to make one or both of the protagonists people of colour – wasn’t taken. Only Keith stands out as a memorable supporting character, and yet he still has the whiff of plot device.

I also felt a mild queasy twinge at the differences in character between Seb – brash, rude, insistently bullying Mia into liking jazz by insisting on ‘educating’ her – and Mia – two quicksteps away from ‘feisty’ but saved by Emma Stone’s beautifully judged performance rather than the words on the page. Gosling tries his best to breathe life into a charming mansplainer (if that’s not a contradiction in terms) and mostly succeeds in at least keeping him just attractive enough a prospect to Mia – even if his singing is shaky. Stone, whose breathy soprano is considerably sweeter, evokes a beguiling combination of fragility and determination, with a warmth that reflects that hers is the character who forms better interpersonal relationships. Despite the fact that Seb has a sister and fellow musicians nearby whereas she only has scatty housemates and dour coffee shop colleagues, he deliberately isolates himself and it is only meeting Mia that seems to draw out reluctant flashes of his humanity. I occasionally got the uncomfortable feeling that Mia’s warmth was characterised as a weakness – that it might be what gets in the way of her goals. Later, female professional success is also represented in terms of family stability; in an overly lengthy coda that fantasises about multiple outcomes, there are none that don’t include two becoming three.

But I said before that, just as the film lacks the conviction to nail its message, its characters and even its format down, I also couldn’t say with determination that I didn’t like it. The full-on wide angle approach is beautiful and used consistently and well. Every visual detail down to costume design is lovingly, colourfully rendered. I’m damned if I’m not still humming one of the songs days later. As a vision, La La Land is stunning, and it is this I think that makes me still excited to see what its director does next. If I could immerse myself in an exhibition like this, I’d fail to emerge for days; on film, it’s just the story that gets in the way.

Disclosure: privately bought ticket for the London Film Festival as a BFI Member. No PR / freebies involved.