The musical - the most heinous abomination of all film genres. There is no excuse for characters suddenly launching into song at the top of their voices. It is, to all intents and purposes, a dead genre, and quite rightly so.

Still, even we have to concede that there are some exceptions; the most tolerable of musicals is of course Grease, with its poppy tunes and breezy outlook to gangs and tight Lycra.

La La Land however, isn't in the same league.

Mia (Emma Stone) is an aspiring actress in LA, currently working in a coffee shop on the lot of a film studio. Sebastian (Ryan Gosling) is a down-on-his-luck jazz pianist, who wants to open his own jazz club.

Mia meets Sebastian. Surprisingly, it isn't love at first sight. However, fate appears to have plans for them, so they do indeed fall in love. But love sometimes isn't always enough; their respective careers, and the directions they take, put extra pressure on their relationship as they struggle to juggle their personal situations.

Director Damien Chazelle is clearly a huge music fan. His last film, the impressive, Oscar-winning Whiplash, followed an exceptional drumming student as he battled with his teacher. His 2009 debut Guy and Madeline on a Park Bench was a love story featuring a jazz trumpeter, so he certainly has form in the musical world. But he's just gone too far this time.

Chazelle has created an affectionate homage to the classic Hollywood musical. There is singing. There is dancing. And indeed singing and dancing. It has a quaint, retro quality that is curiously bearable, for the most part.

And then there are its stars, Gosling and Stone. Gosling is his usual understated but affable self, who manages to ooze charm like other men ooze sweat. Stone is a complete revelation; she's always been borderline likeable, but here she takes it to the next level, with an utterly adorable performance.

After an upbeat first half however, the film begins to stumble and soon drags its feet. As annoyingly bright and breezy as the first section is, the back section is darker in tone, and, well, less musically. If you're going to make a musical, then it should feel like a musical from beginning to end. The latter stages of La La Land lacks the conviction of the tempo set in its earlier part, and ends up feeling like a different film. So despite starting as Hollywood musical revival, it just runs out of steam.

And if we have to sit through a musical, then the songs should be ear worms that will tunnel their way deep into our humbug brains until we can't help ourselves humming them. This film's songs however are instantly forgettable, and won't be popping on any of our playlists any time soon.

The film's success to date is obvious; in this Trumped up era of uncertainty, audiences are clearly in need of escapism of any kind, at any cost. And if that involves characters suddenly singing for no obvious reason, then so be it.

Chazelle so nearly got it right with this film; its infectious retro feel and charming cast are hard to resist, yet it's ultimately let down by an instantly forgettable soundtrack, and a story that just doesn't have the legs to keep the music going all the way to the end. Chazelle's film then wasn't quite worth making a song and dance over.