Penned by I’m Not There writer Oren Moverman, Love & Mercy is a biopic of the Beach Boys’ Brian Wilson, played by Paul Dano, John Cusack and Cate Blanchett. Just kidding.

The film switches between Wilson pre- (Dano) and post- (Cusack) mental breakdown, and the before parts are significantly better than the after – largely due to Dano’s performance as the young Brian in the ’60s; likeable, uncanny and a good singer too. He totally convinces as a musical genius, struggling with psychological, familial and creative forces; he wants to express himself artistically, instead of just writing bubblegum songs about having fun fun fun and surfin’ USA. (“We’re not surfers, we never have been – and besides, real surfers don’t like our stuff anyway!”) The result is Pet Sounds – Wilson’s masterpiece and a highly significant pop album – wonderfully recreated in recording scenes that showcase Brian’s textured arrangements, complex harmonies and experimental techniques; let’s hope those barking dogs saw a share of the royalties or the RSPCA will be pissed. Good good good, good Alsatians.

Wrong album, sorry. The problem is the ’80s strand, which suffers in comparison; not least because Cusack looks nothing like Brian Wilson – or Paul Dano for that matter. His mannered performance fails to convince – whether it’s a case of miscasting or an I’m Not There-style misjudged creative decision, God Only Knows. But it’s not Cusack’s fault; this narrative thread is predictable, melodramatic, and saccharine like bubblegum. The plot sees Brian’s girlfriend Melinda (Elizabeth Banks, great as ever) trying to rescue him from the evil clutches of his therapist/surrogate father/panto villain, Dr. Eugene Landy, wildly overplayed by Paul Giamatti in the worst wig of the year.

That said, the two threads eventually Come Together (wrong band, sorry) in a harmony almost worthy of the Beach Boys themselves. There’s brilliantly trippy direction from Bill Pohlad, a revelatory performance by Dano and ingeniously mixed sound, which emulates the soundscape – the songs, the noises, the voices – rattling around Brian’s moon-faced head. If only the ’80s scenes were as strong; Wouldn’t It Be Nice.