An irresistible Al Pacino plays an aging crooner of flaccid pop crowd-pleasers (I don’t know why Neil Diamond pops to mind). He’s a kitsch pop icon who still fills arenas and rides around in a bus with his face on it. He receives a letter from John Lennon, dated 1971 but lost for decades, saying let’s get together.

As he muses on how different his life and music may have been were he able to say, “Yes, let’s,” he decides to clean up his personal act and reconnect with a groupie-generated son he’s never seen. Oh, the old redemption and reinvention formula, you say. Well, yes and no. It certainly sets up a big, sentimental resolution. Al Pacino doesn’t disappear into the title role as much as ooze into it with comic bravado.

Support includes a spot-on performance by the redoubtable Christopher Plummer as the singer’s manager. And Bobby Cannavale and Annette Bening shine in their admittedly one-note roles. This exuberant, hilarious, and heartfelt movie is not without flaws. Close to cornball in places but never mawkish. At any rate, it’s great to see an all-time great actor back in form. Plot-relevant score by (natch) John Lennon. Japanese title: Dear Danny: Kimi e no Uta. (106 min)