Blow Up is one of my favorite movies—one of those movies that gains prominence in one's mind as somehow more than a movie. It did the same for blossoming young filmmakers in the 1960's, and De Palma's Blow Out is frequently cited as a tribute to Antonioni's film done with sound rather than photography. But Coppola's The Conversation came first, and is both a better film than De Palma's and more true to the spirit of Blow Up.
Made before he'd launched on a career out of playing himself, Gene Hackman plays a soundman who is hired by various parties to confidentially record their conversations. He's the best in the business but his life is a mess—he is intensely paranoid but has nothing to hide and no curiosity about his work. As it turns out, he can't afford any. Just as Antonioni's protagonist sees something he can't confirm in an image he's recorded, Hackman gets trapped by the ambiguity of the spoken word.
Technically, the movie is a marvel of sound engineering. Walter Murch (who did the incredible sound for THX: 1138) is in top form here, and the cinematography is full of empty spaces reflecting the main character's position: my favorite shot is one of his empty loft office, with him shunted off to one side under an industrial-sized lamp.
But the real marvel of the film is the way that Coppola reuses the initial conversation while still finding variety in the camerawork, reaction shots, and angles used. Every iteration brings more information for the viewer, and what could have been a very boring exercise in sound becomes a visual puzzle as well. The melding of the senses is seamless, and Hackman's descent is as well. To the point where many viewers are bored by the film; there are no chase scenes, no dangling out windows, no actual resolution. Because this story isn't about resolution: it's about interpretation and involvement, and Coppola has the sense to step away and let us experience that for ourselves.