Nothing but Hits

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?

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. If even the most iconic songs of a decade often seem rather dated and silly nowadays, the big hits of the summer that were promptly forgotten would be rather painful for the modern audience to experience, what with the evolving aesthetic sensibilities. 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 forty. To use an example: a "love" song from before The Nineties about teenage girls now comes across as stalker-ish, if not outright sexist or misogynistic to a modern adult.

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.

Comic Books

 * The Twelve has twelve World War II characters waking up on 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.

Film - Live Action

 * 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.
 * 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 90's will include Fight The Power by Public Enemy. Buffalo Soldiers, Jarhead and Three Kings all used it.
 * Averted in Zodiac, where most of the contemporary music heard is more obscure than the songs usually used in films set in the 1970s. Ironically, 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 1973-1977 with a "nothing but hits" soundtrack spanning the era. 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 Crystal Skull, the movie starts with Elvis singing the song "Hound Dog". Welcome to The Fifties, folks.
 * Nicely parodied in Tropic Thunder. Seriously, do we ever need to hear "For What It's Worth" in a montage about The Sixties 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, and they're trying to stay in character even after it becomes clear (to us) that the movie's director has been killed and his cast has wandered off the script. Tugg Speedman remains clueless longer than anyone else: even after he's taken prisoner by heroin dealers in the dreaded Golden Triangle, he assumes they're just actors playing Viet Cong.
 * Averted somewhat in American Graffiti; while there are plenty of familiar hits like "Rock Around the Clock" or "Johnny B. Goode", you also get such relatively obscure rock and R&B singles as the Five Satins' "To the Aisle" or the Heartbeats' "A Thousand Miles Away". (Granted, that film was only a decade removed from the period it depicted...)
 * There was an interview with the director of Let the Right One In where he mentioned that he made a conscious effort to avert this trope: although the film is set in the 80s, he didn't want it to be a nostalgic sort of film, so didn't use any period music. Instead, he took the novel approach of hiring a contemporary musician to write a song that sounded like it was from the 80s.
 * Watchmen uses some famous period pieces to date its flashbacks; the way the music combines with the visuals ranges from acceptable to horribly Narmy. The use of Ride of the Valkyries, in particular, is cited as an awkward period film reference. On the other hand, the opening credits, a photo-montage of the in-universe history of superheroes, is set to "The Times They Are A-Changin'", and is nothing short of brilliant. As it is, one song, "All Along the Watchtower" (which is used in a scene set in 1985, by the way), certainly belongs in the film as it is the one song in the film that was used a end of chapter quote in the original Limited Series.
 * However, Ride of the Valkyries is a Romantic work from the nineteenth century. So unless you take the Apocalypse Now connection into account, it's an aversion of the trope.
 * Also, the song had a specific significance in the original comic. This significance had absolutely nothing to do with the scene it was used for in the movie. Also, the comic had several Bob Dylan lyrical quotes in it.
 * It was also referencing the original version by Bob Dylan (as being in print it was more concerned with the lyrics than music). The film chose to use the more popular cover by Jimi Hendricks.
 * John Waters averts the trope in the soundtracks to his historical epics Hairspray and Cry-Baby. John Waters' passion is trolling record stores, collecting obscure regional hits from that time period. Those were from the days when a start-up band could drop a recording to the local radio deejay and make it big. Waters actually released a multi-disc CD collection of some of his favorites he found on his record store journeys. He even mentions in interviews most of his 50s-60s era movies were a love letter to that period in the music industry's history.
 * 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 Janurary 1979 because Peter is preparing to film Being There. (Not to mention Peter died in 1980.)
 * Dazed and Confused both plays it straight and averts it. Most of the tracks featured in the music-heavy film are fairly iconic of 70s rock and well-known today, but several were fairly obscure genre or regional (Southern American) hits.
 * Averted in The Blob where the movie marquee shows them playing Daughter of Horror, a movie most people have never even heard of.
 * A non-musical one: in Back to The Future, 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 1955-56 it regularly got trounced in the ratings by The Perry Como Show in the same Saturday night time slot.
 * An inversion occurs in one of the opening scenes of Back to the Future 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 forgetful, cheesy, 50s monster flicks, but also the first two movies Eastwood ever appeared in.
 * In Precious, which takes place in 1987-'88, Precious' mother is shown watching 227 and an unidentified game show, both of which are not things that people think of when they think of the 80's.
 * Thankfully averted in When Harry Met Sally..., which is set between 1977 and 1989. Instead of contemporary music, the movie uses much older classics by the likes of Sinatra and Bing Crosby.
 * Kind of present but also somewhat averted 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. Present though in the opening scene where Donnie's mother is shown reading It, which is a bit like showing someone reading The Da Vinci Code in a film set in 2007.
 * Mostly averted in Adventureland, where the soundtrack is more obscurish songs and music from the underground of the era, rather than a standard "Greatest Hits of the 80s" type deal.
 * Unless you lived in Australia, where several of those songs were massive hits.
 * The Wackness, set in 1994, largely averts this with a soundtrack of mostly obscure hip-hop songs, rather than a pure Grunge soundtrack one would associate with the era. However, it is somewhat anachronistic, as some of the tracks were not released until after the time period the film is set in.
 * A somewhat odd example happens in The Wackness and Hardball (that Keanu Reeves baseball flick) Where Biggie Smalls is constantly played. Averted in both as the main character in The Wackness constantly carries a walkman with him. And in Reeves in Hardball requests it at a bar.
 * Semi-averted in The House of the Devil, which isn't set in the early 80's so much as it is specifically designed to look and feel like it was originally filmed during that period. Three 80's singles are listened to by characters. "One Thing Leads To Another" by The Fixx is well-remembered enough to show up on many 80's hits compilations. On the other hand, "One Of Our Submarines" by Thomas Dolby and "The Breakup Song (They Don't Write 'Em)" by The Greg Kihn Band are a bit more obscure. All three of these songs were released within a few years of each other and would place the film around 1983 or so. And then the soundtrack also uses much more recent music by Gods Of Fire, which is just influenced by 80's metal enough to not stick out too much.
 * The Wood has 80's 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 Oyster 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. 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).

Live Action TV
"Carol Twilling: Does everybody like Santana? Sam: Oh, God. [* everyone stares at him* ] ...God, I love Santana."
 * Nearly everyone in Life On Mars listens to The Who, Led Zeppelin, Cream and Lou Reed. Never Chicory Tip, The Osmonds, Lieutenant Pigeon or Gilbert O'Sullivan. For those who don't understand, the latter bands all had #1 hits in the '70s... but don't get airplay today outside of syndicated reruns of American Top 40.
 * And Gilbert O'Sullivan is actually featured at the end of a 2nd season episode. A very depressed Sam watches him sing "Alone Again (Naturally)" on TV -
 * The U.S. version also used Gilbert O'Sullivan in its first few weeks, but played "Get Down" instead of "Alone Again (Naturally)".
 * Another possible example from the same episode, depending on how you feel about the band in question:


 * The sequel, Ashes to Ashes has the characters driving the (then) very new- and presumably expensive- Audi Quattro. An icon of 80s nostalgia perhaps, but one suspects they would really have been driving something like a Ford Granada or Cortina, or possibly some 70s-derived model from British Leyland. Of course it happens in the characters' heads, so if that's how they remember the 70's/80's (as most people do), it's a Justified Trope.
 * 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 Glenn Miller did not even compose until 1941, in an episode centered around the 1938 broadcast of The War of the Worlds
 * Averted in one episode where plot-related and heard in-universe song was composed specially for show.
 * Subverted (like so much else) in Mad Men, which leans towards gooey big band and forgettable novelty songs of the late 50s: the few exceptions tend to be blatantly anachronistic, as with the use of Bob Dylan in the season 1 finale.
 * Starting in Season four, the soundtrack becomes way more contemporary but, with a few exceptions, still fairly obscure.
 * 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*
 * In "Father's Day", Pete's car radio plays several hits of the late 80s, including "Never Gonna Give You Up".
 * An early William Hartnell serial showed the characters watching a clip of The Beatles (then contemporary with the show) performing on aonther BBC show, because one of his companions - a girl from far in the future - was curious about them.
 * "Paperback Writer" by The Beatles was heard in a scene from the Patrick Troughton story "The Evil of the Daleks" when the Doctor wanders into a contemporary coffee bar, and "Oh Well" by Fleetwood Mac accompanies a factory scene in the Jon Pertwee story "Spearhead From Space". There are many others throughout the show's long history.
 * Freaks and Geeks did an excellent job at averting this.
 * Smallville episode Relic has a series of flashbacks set in the '60s, and at one point the song "Earth Angel" is playing from a car radio... in a scene involving an alien (Jor-El) and his new human girlfriend (Louise).

Video Games

 * BioShock (series) used a lot of famous music that people are likely to recognize as being from the 40's and 50's -- the game itself takes place in 1960. A lot of the songs were hits, like Papa Loves Mambo and La Mer, but it's also possible that it's an aversion inasmuch as few people are likely to have heard many (or any) of these songs.
 * 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.
 * Back during the "Introspective Vietnam FPS" craze, many companies invoked this trope. Seeing as how a great deal of developers probably weren't born until the tail end of the war, it should be easy to see why they wouldn't think of adding in stuff that wasn't easily available on a Greatest Hits compilation.
 * Used as a plot point in Metal Gear Solid Peace Walker; Big Boss obtains a recording of his mentor's voice talking to an Englishwoman he doesn't recognize. The only problem is that in the background of the recording, the Live In Japan of the song "Sing" by The Carpenters is playing, a song that was a hit in 1974, and his mentor died in 1964.
 * The soundtracks of Grand Theft Auto: Vice City, San Andreas and Vice City Stories are all heavily stacked with hits from The Eighties (in the case of the former and the latter) and the early '90s (in the case of San Andreas).
 * Averted with several songs, which may sound and feel like the 80's/90's, but are not necessarily widely remembered hits, many being acts that are majorly unknown for people who didn't live in that time period.
 * Averted with the game version of The Warriors, which in addition to the songs from the movie itself (which are themselves quite obscure to most post-Seventies audiences, with the exception of the cover of "Nowhere to Run") also has catchy - but not well-remembered - disco and pop songs that were only minor hits at the time the narrative is taking place (1978-1979). The list of artists includes Mandrill, Love Deluxe, Vivian Vee, and others whom only diehard fans of Seventies music will ever even have heard of. There's even a slightly anachronistic punk song on the soundtrack that is actually from the early Eighties, but sounds like it could be from the Seventies.

Other

 * One curious aversion exists: in shows and movies set during the 1960s, you are unlikely to hear anything performed by The Beatles on the soundtrack, and if you do hear Beatles songs at any point they're more likely to be covers than the originals. This is partly because the Beatles' music is both costly to get the rights for and for the most part closely guarded as to what projects will be allowed use of their songs. But considering how they were and are pretty much widely considered the iconic band of the 1960s, and how popular and widely played their music was and still is, it can be curious listening to something presenting nothing but the 'hits' of the 1960s with this rather large omission in mind.
 * I Am Sam uses nothing but Beatles songs on the soundtrack, but a) It's set in the modern day (the main characters happen to be fans), b) all the songs are covers, and c) many of them are the "deeper" cuts from the group's albums rather than the huge radio hits.
 * This BBC article discusses the 'Unswinging Sixties' after Radio 2 played a chart of the best selling music of the decade. Music including Ken Dodd, Engelbert Humperdinck, Frank Ifield, The Seekers, and Rolf Harris.
 * Speaking of the BBC, their own Sounds Of The Sixties programme on Saturday mornings averts this trope rather thoroughly; they have an absolutely massive recorded music library, and the show makes a speciality of playing the lesser-known stuff.