If your show is set after 1930, then at some point a radio will be heard. It will only be playing well-known songs that, with hindsight, are seen as the coolest or most iconic of their era. Never any of the novelty singles, one-hit wonders or any form of teen pop that would have been on genuine radio stations of the period. If a movie marquee is seen, it will be showing a well-known classic of the period. Newspaper headlines will be the stories that everyone remembers, and televisions will always be showing either a famous opening sequence (M*A*S*H, The Mary Tyler Moore Show, etc.) or a famous scene (such as the chocolate factory scene from I Love Lucy).
As a corollary, the radio will almost always be playing current hits of the period in question, especially if the scene is a flashback set 10 years or more before the main action of the show. How would the audience know the flashback is taking place in 1982 if the people in it are inconsiderate enough to be listening to hits of the '60s or '70s on an oldies station, or of 1987?
In addition to giving a clear indication as to the time period of a scene, this allows the audience to only be exposed to elements of pop culture that have aged relatively well. After all, if even the most iconic songs of a decade often seem rather dated and silly nowadays — due to changing tastes, Values Dissonance, etc. — then the throwaway hits of a given summer that were promptly forgotten would be rather painful for a modern audience to experience. Unless they are deliberately picked from the worst of the worst. Oldies radio stations in the real world do the same thing: What you loved when you were 15 is different from what you want to hear on an oldies station when you are 40. To use one common example: many a "love" song written from a male perspective prior to The '90s now comes across as stalker-ish, if not outright sexist or misogynistic, in its attitude toward women when heard with modern ears.
Of course, the above doesn't apply just to period pieces. Vintage films set in their contemporaneous times (especially if they're from The '80s or later) will more often than not have a soundtrack consisting of current pop songs for the tie-in merchandising, and in hindsight they will themselves come off as this trope. (Consider the embarrassing VHS description for the 1984 musical Purple Rain, which was not updated for the DVD rerelease more than a decade later: "...a now soundtrack by the hottest bands around!") note
This is likely to occur in a "Mister Sandman" Sequence, though in that case the song would likely be playing on the film's soundtrack rather than within the scene itself. A sub-trope of Small Reference Pools. Related to Nostalgia Filter and Popular History. Can overlap with Politically Correct History if the vintage element being shown is popular now, but was way too avant-garde or even offensive in its own era for most people to enjoy it.
- In the Kia Optima ads featuring NBA player Blake Griffin, he time travels to his past selves (in 1995, 1997, 1999, 2002 and 2006) to brag about his new Kia, and also to hint that he will play basketball in the future. Whenever he time travels, the car radio plays a big hit from the year he travels to. For example, the 1995 one plays "This Is How We Do It" by Montell Jordan and the 1999 one plays "Blue (Da Ba Dee)" by Eiffel 65.
- The Twelve has twelve World War II characters waking up in the 21st century. They're put in a fake '40s hospital to avoid culture shock during their recovery, complete with a radio playing '40s hits. The first suspicion that something is wrong comes when one of them notices the radio is not playing commercials.
- The movies Forrest Gump and Remember the Titans used only well-known songs in their soundtracks, and a hell of a lot of them; there are enough songs included that roughly 90% of each movie contains a hit song, and no two scenes in either flick re-use the same tune.
- Except for the times when it's in-universe in Remember The Titans, such as when the team sings "Ain't No Mountain High Enough" or "Na Na Hey Hey Kiss Him Goodbye".
- Remember the Titans also plays with this trope. When things look bad for the Titans, the film's original score is used. When things begin to look better, then they start to use late '60s/early '70s classic rock.
- In Apollo 13 the teenage daughter's radio was playing during almost every scene they showed Lovell's family, clearly to sell yet another late '60s/early '70s classic rock movie soundtrack.
- Many movies set in the very early '90s will include Fight The Power by Public Enemy. Do the Right Thing (1989), Buffalo Soldiers, Jarhead and Three Kings all used it.
- One of the cuts David Fincher made to Zodiac before it hit theaters was a blank-screen audio montage that denoted the passage of time between 197377 with a "nothing but hits" soundtrack spanning the era, though it does not appear in the final version. The Director's Cut restores this, utilizing well-known songs by Roberta Flack, Wild Cherry, Bachman Turner Overdrive and other ubiquitous hits.
- Many biographical musicals use Nothing But Hits to the point of anachronism.
- In Indiana Jones and the Kingdom of the Crystal Skull, the movie starts with Elvis singing the song "Hound Dog". Welcome to The '50s, folks.
- Parodied in Tropic Thunder. Seriously, do we ever need to hear "For What It's Worth" in a montage about The '60s again? Ironically, the scene in question is actually taking place in roughly our own time. The main characters are actors filming a Vietnam War story on location in Southeast Asia.
- Plenty of familiar hits like "Rock Around the Clock" and "Johnny B. Goode" can be heard in American Graffiti, though there are also such (now) obscure rock and R&B singles as the Five Satins' "To the Aisle" and the Heartbeats' "A Thousand Miles Away". (Granted, that film was only a decade removed from the period it depicted...)
- Watchmen uses some famous period pieces to date its flashbacks. For example, in the opening credits, a photo-montage of the in-universe history of superheroes, is set to "The Times They Are A-Changin'".
- Played straight several times in The Life and Death of Peter Sellers, namely the sequences set in the 1960s and '70s...as noted at the link, they are anachronisms in relation to the events depicted. One not mentioned anymore at IMDb is the use of The Clash's "Should I Stay or Should I Go", from 1982, in a scene that cannot be set any later than early January 1979 because Peter is preparing to film Being There. (Not to mention Peter died in 1980.)
- Dazed and Confused. Most of the tracks featured in the music-heavy film are fairly iconic of '70s rock and well-known today.
- Back to the Future
- A non-musical one: in the first film, Marty spends his first night in 1955 with his mother's family, watching an episode of The Honeymooners. Of course, one reason why The Honeymooners only lasted 39 episodes as a standalone sitcom is that in the fall and winter of 195556 it regularly got trounced in the ratings by The Perry Como Show in the same Saturday night time slot.
- Invoked by the Cafe 80s store Marty enters in Back to the Future Part II, as the cafe is deliberately going for the '80s throwback aesthetic and as such has "Beat It" playing when he walks in.
- An inversion occurs in one of the opening scenes of Back to the Future Part III, Marty comes out of the restroom at a drive-in theater dressed like a cheesy 1950s cowboy. He comments that he doesn't think Clint Eastwood would ever wear such a thing, and Clint Eastwood is the name he chooses to go by for the rest of the movie. When he says this, he gestures to the movie posters showcasing what movies are currently showing at the drive-in. The two movies are Revenge of the Creature and Tarantula!, two '50s monster flicks, but also the first two movies Eastwood ever appeared in.
- Played straight in an ironic sort of way in Pleasantville, where we hear Buddy' Holly's "Rave On" on a jukebox at exactly the time (April 1958) and place (a teen hang-out) that song would have been heard in real life — but probably NOT in Pleasantville, where anything the least bit unorthodox or controversial (which rock and roll certainly was back then) literally didn't exist.
- Subverted in Donnie Darko. It does use some '80s nostalgia tracks like "Head Over Heels" by Tears For Fears but also some more obscurish songs like "The Killing Moon" from Echo & The Bunnymen. Most of what's shown on TV is coverage of the 1988 election and the film shown in the theater is a double bill of The Evil Dead and The Last Temptation of Christ rather than some current film.
- A somewhat odd example happens in The Wackness and Hardball (that Keanu Reeves baseball flick), where The Notorious B.I.G. is constantly played.
- The House of the Devil, which isn't set in the early '80s so much as it is specifically designed to look and feel like it was originally filmed during that period. Three '80s singles are listened to by characters. "One Thing Leads To Another" by The Fixx is well-remembered enough to show up on many '80s hits compilations. The other two singles, "One Of Our Submarines" by Thomas Dolby and "The Breakup Song (They Don't Write 'Em)" by The Greg Kihn Band, on the other hand, are a bit more obscure.
- The Wood has '80s rap and R&B hits during the flashbacks to 1986.
- Let Me In (the American remake of Let the Right One In), set in 1983, indulges in this with songs by Culture Club, David Bowie and Blue Öyster Cult playing in the background.
- Oliver Stone's Born on the Fourth of July opens in the suburban community of Massapequa, New York, in the year 1956. The characters are attending a Fourth of July parade, and from one of the floats Bill Haley and the Comets' "Rock Around The Clock" can be clearly heard (and there's also a shot of some greaser guys and girls sulking at the edge of the crowd, glaring at everyone). Surprisingly, no one among the families (with many children) lining the street seems to find this at all offensive (which is especially striking because Stone later goes out of his way to show that these working-class suburbanites are extremely socially repressed).
- Take Me Home Tonight runs on this trope as you can guess from the title (it was also titled "Kids In America" at one point).
- Iron Man 3 opens with "Blue (Da Ba Dee)", heralding a flashback to New Year's Eve, 1999.
- X-Men Film Series:
- X-Men: Days of Future Past: All your favorite tunes from the The '70s. The first thing Wolverine hears in 1973 is Roberta Flack's "The First Time Ever I Saw Your Face"; Quicksilver listens to Alice Cooper's "Hello Hooray" and Jim Croce's "Time in a Bottle"; the disco in Paris is playing Claude Francois's French '70s hit "Stop au nom de l'amour."
- X-Men: Apocalypse: The song selection leaves no doubt that the story is set in The '80s. Metallica's "Four Horsemen" plays when Archangel is "born," and the Eurythmics' most famous song, "Sweet Dreams (Are Made of This)," is heard during Quicksilver's rescue of Xavier's students. Both were released in 1983. An Egyptian cover of A Flock of Seagulls' "I Ran (So Far Away)," a smash hit in 1982, is blaring from a boombox at the Cairo market. Men Without Hats' "The Safety Dance," another classic from that year, accompanies the deleted mall scene.
- The Big Chill and its use of vintage Motown songs to the point of making oldies cool again.
- Everybody Wants Some!! is meant to be a Spiritual Successor to Dazed And Confused but set in 1980, so fittingly it has a similar mix of iconic late seventies to early eighties hits.
- Guardians of the Galaxy has main character Peter Quill listen to the Awesome Mix Vol. 1, a mixtape of his mother's favorite songs from the '70s. Because it's a greatest hits mixtape, of course, it plays this trope hard, with songs such as "Escape (The Pina Colada Song)", "Ain't No Mountain High Enough", "I Want You Back", and "Spirit in the Sky". (There are, of course, lesser known songs like "Hooked on a Feeling", "Ooh Child", and "Come and Get Your Love".) The sequel averts this trope a little harder.
- Christine uses this as a sign that there's something wrong with the car in question. Even set in the mid-1980s, the red Plymouth Fury plays music straight from the '50s.
- The NBC miniseries The 60's and its sequel The 70's are this trope.
- Nearly everyone in Life On Mars listens to The Who, Led Zeppelin, Cream, Lou Reed and Santana, well-remembered bands of the '70s. (One key exception being Gene Hunt, who hates rock music but will quietly admit to liking Roger Whittaker.note )
- Cold Case's flashbacks use only well-remembered hits to help define the feeling of the historical period. With period settings, this can skew toward the anachronistic, since they once used Glenn Miller's "String of Pearls", which Jerry Gray, its composer, did not even write until 1941, in an episode centered around the 1938 broadcast of The War of the Worlds.
- Averted in one episode where a plot-related and heard in-universe song was composed specially for show.
- Doctor Who isn't known for featuring music or TV shows of the day (with a few present-day exceptions), but in the serial "Remembrance of the Daleks" (set at the time that the very first Doctor Who story aired IRL), Ace leaves a room and the camera cuts to the next scene just as the TV announcer is introducing "a brand new science-fiction show called Doctor..." *click*
- American Dreams used this motif while actually playing the songs live as they happened on American Bandstand, with Guest Stars as the singers of the day. (Of course, a few of the songs were never played on Bandstand). The show was notorious for its musical anachronisms. The very first scene in the entire series features Stevie Wonder's "Uptight (Everything's Alright)" playing while the caption reads, "Philadelphia, 1963"... not only three years before the song we're hearing was recorded, but arguably the biggest three-year gap of the rock era in terms of how music changed.
- The 2002 adaptation of White Teeth uses a number of hit songs contemporary to the setting of each episode (197492); mainly non-diagetically for dialogue-free scenes, and in the opening titles and end credits.
- Everybody Hates Chris epitomizes this trope, it takes place in the '80s (198287 to be precise) and almost every single popular '80s song you can think of is heard at some point.
- Averted in the first episode of Stranger Things where Benny the diner owner is playing Jefferson Airplane, but not "White Rabbit" or "Somebody To Love" as one might expect, but the less well-known "She Has Funny Cars" from the same album.
- The Goldbergs ends each episode with a scene set to an 80's hit, sometimes relavant to the plot of the episode.
- Can be Truth in Television with so-called "Top 40" and "All Hits" radio stations, which only play songs from the Top 10 or so of the current chart in heavy rotation while less popular songs only come up occasionally.
- Oldies, classic hits, and classic rock stations generally play this straight as well, airing only the biggest and most durable hit songs from the nostalgic eras they cover. You may hear the occasional "deep" album cut on rock-oriented stations, however.
- BioShock used a lot of famous music that people are likely to recognize as being from the 1940s and '50s — the game itself takes place in 1960. A lot of the songs were hits, like Papa Loves Mambo and La Mer.
- The Fallout series is set in an alternate universe post-apocalyptic 1950s with many references to '50s culture, including a collection of period appropriate songs, most prominently featured in Fallout 3 where the player can tune into Three Dog's radio show for some easy listening while wandering the Capital Wasteland.
- Mafia III nicely subverts this. Lots of iconic songs from the late '60s appear, however there are plenty of more obscure ones and songs that were popular at the time but largely forgotten. Many songs from earlier in the decade and the '50s also appear. Overall the radio stations provide a pretty believable experience.
- Grand Theft Auto also subverts this, with the appearance of hit music usually lower or equal than the obscure and dated music of its appropriate era. They did, however, in occasion play it straight in Grand Theft Auto III for one of the radio station exclusively plays tracks from Scarface OST.
- Metal Gear Solid V: The Phantom Pain uses this heavily, being set in 1984 and having radios set around guard posts playing mostly hits from the '80s that still haven't aged and inexplicably on the hands of Soviet troops.