This comes through, a little, in the film's music, by James Murphy, which captures the feel of Los Angeles studio pop of the late 60s and early 70s—I thought, like P'fork did, of Harry Nilsson, though I really could have used a song like his "Everybody's Talking," from noted post-studio auteur film Midnight Cowboy.
But it's especially a matter of the cinematography, by Harris Savides.
Savides is responsible for the film's distinctive offhanded, smoggy look, which is "naturalistic" not in the fashion of contemporary DV photography, but an the older fashion, like you can tell from the grain that you're watching real things shot on real film. (Contemporary technology shapes our ideal of a "neutral" aesthetic.) I'm not sure, but it looks like Savides used a lot of telephoto lenses, for those flattened man-walking-down-the-sidewalk-surrounded-by-seas-of-smeary-people shots, the ones 70s directors of urban-set features used to shoot from a distance, back when movie stars and regular people were permitted to mingle. (In Bordwell and Thompson's Film Art: An Introduction, they use stills from Tootsie.)
(You can also detect a more European-seeming 70s feel to Savides's work on Baumbach's Rohmer tribute Margot at the Wedding—and for that matter in Robert Yeoman's handheld 16mm photography of the Eustache-quoting The Squid and the Whale.)
I could go on in this vein, but I don't need to, because David Schwartz, of the Museum of the Moving Image, has just conducted a wonderful long interview with Savides, in which they discuss Savides's work on many of the most distinctive-looking films of recent years (The Yards! Gus Van Sant's death trilogy! Zodiac!), and on the influence of many of the great European cinematographers who helped developed the look of the 70s' New Hollywood cinema. (Like Vilmos Zsigmond, who shot Long Goodbye.) If you read just one wide-ranging piece about the art, craft and history of cinematography today...