Toe-Tapping Melody

Someone in a fictional work starts playing a tune. In most musicals, people either join in or serve as the background characters. Then you have a song that inspires people to join in, listen, or even clap. You can feel the joy.

Toe-Tapping Melody is one that inspires a nearby audience or individual to follow along, either by joining in to sing, clap, or acknowledge that it's a catchy melody. It may overlap with Ear Worm if the individual cannot get the song out of their hand. Participation or commentary is key to this trope.

How is this different from a Crowd Song or Audience Participation? Because in-universe, the crowd song or participation may not be spontaneous. Or it can be as little as someone singing along, tapping to the beat, or bobbing along.

Note: The TV Tropes version of this is called Actually Quite Catchy. I don't like this one because it equates the trope with "Actually Pretty Funny". Happy to brainstorm another title as well.

Advertising

 * In an award-winning anti-smoking ad, several teens go to confront tobacco executives about the hazards of nicotine. The business executive starts a musical number to "Just Focus on the Positive"; the teens can't help but join in with the number, and drag in the various background extras, including paramedics, nurses, and hospital patients. Yes, that includes the dead ones..

Anime and Manga

 * Played to horrifying effect in a Junji Ito one-shot where a musician plays a screaming melody asking someone to leave her alone. Anyone who hears it can't get it out of their head. Some may hum along. A doctor reveals that the melody is a manifestation of the musician's stalker ex-boyfriend, that died by suicide in front of the musician.
 * The youma in a Sailor Moon episode invoked this by using a soundwave that compels anyone who hears it to want to perform.

Ballads

 * Ballads by design are supposed to be shared by singing them. They are meant to be passed on word-for-word, and being catchy certainly helps with being memorable.

Comic Books

 * In Raina Telgemier's Drama the song that Maybelle sings with the leading role in Moonlight Over Mississipi is supposed to invoke this. It's the moment where she and the Union general have their first kiss, building up the dramatic tension. Callie is always entranced when Jesse sings it, partly because she has a crush on him..
 * Played for awesome drama in Sandman whenever Orpheus sings. Anyone who hears the music is compelled to listen to it, whether they want to or not, and thus Orpheus can be dangerous if he has aggressive intentions. The French revolutionaries can attest to that when they attempt to destroy Orpheus's head, and he sings to save himself and Johanna Constantine.

Film

 * In Aladdin, this happens a few times:
 * When the genie sings "Friend Like Me," Carpet wastes no time in dancing along, complete with a top hat and cane! He and Genie have a history, given their handshake, so he's well-acclimated.
 * During "Prince Ali," Jafar is unamused that yet another chump prince entourage interrupted his plan to hypnotize the sultan to marry Princess Jasmine. Iago, however, likes the music and starts dancing. He stops when Jafar glares at him. Jasmine at first watches with mild interest, but she does a Face Palm when "Ali" shows off his muscles for women ogling him from a balcony. While Razoul doesn't like this prince, his guards happily join in for the last few verses.
 * This also comes up during the three-quel Aladdin and the King of Thieves
 * In "There's A Party here in Agrabah", Genie hypes up the city crowds and guests as he goes around putting the final touches to his friend's wedding, while he is the best man and wedding planner. While some guests are less than amused, given he turns their hairstyles into giant afros, some of the locals are belting loudly. The Forty Thieves also join in for a verse, and shout, "They're finally getting married!" to a disguised Kaseem's confusion.
 * Iago gets into "Welcome to the Forty Thieves" when he sees how much loot they store. They quickly rip him away when seeing he's getting too attached to the money.
 * The live-action Aladdin has this happen as well:
 * Genie invites Aladdin to dance with him during "Friend Like Me". While at first he puppeteers Aladdin along, Aladdin starts getting into the dancing for real without needing cues.
 * The crowds of Agrabah, the Sultan, and Dahlia get into "Prince Ali" when the Genie ushers in a disguised Aladdin, complete with an entourage. Dahlia nods in approval as Genie starts the first verse, and starts bopping along as Jasmine stares with amused confusion.
 * The movie has a Dance Party Ending with a Triumphant Reprise of "Friend Like Me" at the double-wedding for Aladdin and Jasmine, as well as . Carpet does the Carlton while Aladdin plays flute, and all the major cast members do one last dance line.
 * Parodied in Enchanted. When Giselle starts a Crowd Song in Central Park, lawyer Robert is bewildered that people keep joining in randomly. He asks how a bunch of musicians know the song that just started. The sign that Gisel is starting to acclimate to New York life is when her fiance finds her, and she doesn't know the lyrics to the song he sings, "I've Been Dreaming."
 * In The Great Mouse Detective, there are two moments from the Villain Songs, to boot:
 * Most of Ratigan's mooks sing out of fear what he will do if they step out of line or show their discontent. When poor drunk Bartholomew calls Ratigan a "rat" while hiccuping, Ratigan sentences him to death by Felicia. Bartholomew keeps singing as he is swallowed alive. Before his coworkers can mourn him, Ratigan orders them to resume singing, threatening to summon Felicia again with his bell.
 * A stripper in the Bad Guy Bar where Ratigan's hideout is located manages to quiet the angry mob just by singing. They put down their chairs that they were going to toss at the stage, and become emotional as she belts to the "Dearest gentleman". When she strips to a blue slip, they really get into it. Dawson, who gets drugged, somehow hops onstage and joins her backup dances for the can-can line. Even Fidget sings along as he navigates through the tunnels to Ratigan's lair.
 * Subverted hilariously during Hoodwinked. When the Wolf, Granny, Twitchy and the Woodcutter witness, Granny comments, "We gotta do something!" Wolf agrees because the rhythm and dancing were way off for the musical number though the song was good.
 * Happens during Lilo and Stitch. During the fight with Stitch in the Pelekai household, Jumbaa turns the record-player on by accident. He starts swaying to the rhythm of "Hound Dog," giving Lilo and Stitch an opportunity to convene in the kitchen.
 * Tangled shows a contrast of this during "I've Got A Dream"; as Flynn watches with bemusement while Rapunzel defuses the bar patrons. She asks them to sing about their dreams, and dances with them. While Flynn needs to be threatened at knifepoint to sing as well, several rats are bobbing along to the music, as a confused Pascal observes.

Literature

 * In the Discworld novel Soul Music, that this happens is a plot point. Music with Rocks In turns Imp into Buddy, a spoiled diva musician that forgets his harp background when he plays a magical guitar from a mysterious shop. Susan notes that the music itself kept him alive past when his hourglass was supposed to shatter..

Live-Action TV

 * Brooklyn Nine-Nine has a Cold Open where Jake has a witness evaluate a criminal lineup. She didn't see the criminal, but heard him singing "I Want It That Way" while hiding from him. Jake has each of the suspects sing a line from the song, but they all turn out to be great singers. He gets into it, shouting, "TELL ME WHY!" and getting excited when they all join in harmony..
 * Buffy the Vampire Slayer has an episode where Giles requests a night off from watching the Scoobies for adult time. He asks them not to bother him, bar any threatening emergency. Sure enough, an emergency happens so the Scoobies go and find him playing guitar at a cafe. While Xander is horrified, and Buffy is later after she hears about it, Willow smiles and says she remembers why she had a crush on him when he was the school librarian.
 * Drake and Josh:
 * "Blues Brothers" features Josh suffering from stage fright, just as Drake's band prepares to play for a talent show. Drake is displeased to find out that a rival a capella group stole his song to perform. Josh gains the courage to perform "Soul Man" with Drake's band, and his performance wows the crowd, as well as the judges. Even Jerkass Megan sings along and is visibly proud of her brothers.
 * The series finale "Really Big Shrimp" centered around a music company buying one of Drake's songs. During the A plot, a producer remixed it for the Super Bowl so terribly that Drake in revenge filled his car with fruit flies and Josh quickly switched the recording with the original. When the producer's boss heard about this breach of contract, he let the boys off the hook because the original song when viral, and he agrees that the remix was terrible. Helen asks Drake to perform it at her wedding after Eric and Craig accidentally burn down the movie theater.
 * Scrubs
 * Turk sings "I'm gonna cut you open" when he learns he's been assigned to do J.D.'s appendectomy. He enters the room dancing, and Carla joins in with him. Naturally, this doesn't ease J.D.'s fears about his best friend being a goof about a life-threatening surgery.
 * Ted's a capella group practices at the hospital from time to time, going from theme song to pop music covers. While J.D. tries to avoid them on the night shift, Carla enjoys seeing them and dances along. A season 7 episode has Ted woo a woman named Stephanie Gooch by inviting her to jam on ukelele with his group, and they do a beautiful rendition of "Carry On, My Wayward Son". J.D. and the Janitor, who have called truce to help Ted talk to Gooch, stop to admire the group jam.
 * "My Way Home" has Dr. Cox, as part of a prank on J.D. involving the new intern Keith, has Keith call him to the hospital on one of his days off while Laverne's church choir sings "Payback is a bitch!" Keith starts bobbing along to the song, until J.D. levels a Death Glare at him.
 * "My Musical" reveals that all the song and dance numbers that Ms. Miller was seeing was

Music

 * Amanda Palmer encourages this from her audience. Many YouTube videos show her cheering on the audience to sing along if they know the words, and even if they don't. When they memorized her "New Zealand" song from YouTube, she apologized to them for changing the lyrics over a year.

New Media

 * Many Let's Players have sung or danced along to songs in video-games:
 * Jacksepticeye has bobbed along to the Cuphead and Undertale boss music. There's a video of him singing "A shimmy shammy" while playing different versions of Super Mario Bros.
 * Markiplier has sung along to Mettaton's song in his Undertale stream with Tyler, breaking down laughing at some of the later lyrics. He's also made up lyrics to go along with.
 * The Fine Bros. Entertainment "Try Not To Sing Along" challenge features this for its participants. FBE employees, old and young, need to listen to popular songs and are not allowed to sing along, hum, move their lips, clap, or even so much as tap in rhythm to the music. One deleted video showed that Spongebob Squarepants is super-catchy and hard to resist.

Newspaper Comics

 * Mentioned in a one-off gag in Pearls Before Swine. Zebra says that his herd on the savannah has been using musical alarm bells for warnings about predators. When they go off, the herd sings along.

Oral Tradition, Folklore, Myths and Legends

 * Hindu Mythology:
 * Krishna when a cowherd boy could induce the local gopis and cows to dance when playing his flute. When he had to leave his village home to face Kamsa, a village girl named Radha asked him to leave behind his flute, so she could always remember him.
 * Meerabai or Saint Mirabai was a Krishna devotee who declared the avatar was her husband, even though she lived hundreds of years after his time. She wrote many hymns and poetry dedicated to Krishna. The Amar Chitra Katha comic depicting her life shows her leading entire groups of devotees into songs.

Puppet Shows

 * The Muppet Show
 * Statler and Waldorf occasionally admit this. One time, Statler actually applauded for Kermit performing "Lydia the Tattoeed Lady".
 * When Harry Belafonte performed "Turn The World Around," the entire Muppet show cast and crew joins him onstage for the last round of verses. Kermit lampshades that they don't want this perfect moment to end. Statler and Waldorf, who normally snark about how terrible the show is, also sing along!
 * Sesame Street
 * If Luis brings out his guitar, expect any nearby Sesame Street cast member to either listen to his song or join in on the tune. One sweet episode has Rosita becoming so inspired by his music that she asks for guitar lessons.
 * A musical guest will often perform and attract everyone's attention on Sesame Street. Highlights include Stevie Wonder, Denyse Graves, Little Richard, and Queen Latifah.

Recorded and Stand Up Comedy

 * John Mulaney describes that you can take this trope too far in his infamous "Salt and Pepper Diner" monologue. He and his friend John, another John he quickly clarifies, thought it would be funny to put in 21 requests for "What's New Pussycat," with one "It's Not Unusual" tossed into the jukebox at the diner. While the patrons at first didn't notice, they realized the song was going on, and not ending. One person even screamed, "Goddammit!" after it started up for the fifth time.

Theatre

 * Hatchetfield has this happen a few times in its various shows:
 * The Guy Who Didn't Like Musicals
 * Beanie's manager Zoey makes her employees do a new tip song. Emma is not into it, having to sing and dance for fifty cents, but doesn't want to get fired. While she's unenthusiastic, the coffeeshop patrons sans a very terrified and confused Paul enjoy the music. That is, until the patrons take a sip of their fresh coffee, choke, and collapse to the ground as the music becomes menacing when Emma threatens to quit. Turns out the singing zombies got to Nora and Zoey, and they poisoned the coffee with "blue shit" that turns everyone who drank it into a singing zombie.
 * Professor Hidgens plays his demo songs of Workin' Boys to a . While Emma is practically crying with frustration because, Ted bobs along and asks Professor Hidgens to hit them with another song.
 * "Honey Queen" has Linda and Gerald Monroe use a few hundred dollars and the Homeless Guy to get Zoey to belt at her coffeeshop job, by stuffing her "Tip For A Song" jar. Apparently Zoey fires up the whole coffeeshop in her attempts to impress who she thinks is a Broadway producer. Only problem is she blows out her voice and can only croak the next day, just as the talent show is starting.

Video Games

 * Some hilarious examples are in Undertale:
 * You can put on some ghost tunes at Napstablook's house. They say that they love the rhythms and vocalizations. Put on "Spooktunes" and leave, you will encounter a freaked-out Aaron and Woshua. They don't bother fighting because the music scares them into fleeing. As a Brick Joke,.
 * If you want to give Shyren lots of love, you can keep singing with her. You start a band with her, that gets popular as Sans tosses toilet paper and socks at you. She's so catchy that the Golden Ending features her . The hitch is that it's easy to die to her, because the more confident the get, the more "musical note" bullets she will send your way.
 * In Night in the Woods, Mae rejoins Gregg and Angus's band when she returns home. Germ, a local teen, is their only fan, but he adores their rehearsals. Mae enjoys performing even if you mess up badly during the rhythm games.

Web Animation

 * Discussed in the Homestar Runner "Strong Bad Emails" section. The "Rampage" video has Strong Bad attempting to do a musical rampage with Coach Z. Strong Sad politely interrupts to ask how Strong Bad reciting, "I'm on a rampage" on loop is musically inspiring. He says there's no rhythm or variety to it. Strong Bad challenges him, saying Let's See You Do Better. As the Cheat lays out a beat, Strong Sad recites a poem: "The quill, the page, lyric rampage. Word up?" This causes Coach Z and Strong Bad to giggle because they don't see anything catchy about it; Strong Sad reveals that it was a hit at his slam poetry group.

Web Comics

 * Check, Please! (webcomic) often showcases Bitty's love for Beyonce as a Running Gag. His roommates often hear him singing and dancing along to Beyonce in the shower. Insulting Beyonce is a good way to get on Bitty's bad side.

Western Animation

 * In the Avatar: The Last Airbender episode "The Cave of Two Lovers," several wandering nomads treat the Gaang to Sacred Hospitality as they encounter each other, braiding Katara's hair and adorning Aang with flowers. They also sing about a Secret Tunnel nearby that they plan to navigate. Aang and Katara get into the song and bob along, while Sokka is frustrated and wants to move on with their journey. Quite ironically, he learns that the nomads' music leads to the safest way to navigate the tunnels: badger-moles use earthbending to change the tunnels and singing to them convinces them to lead a path outward.
 * Comes up in Justice League Unlimited in the episode "This Little Piggy". Circe turns Wonder Woman into a pig out of spite; while the League goes to find Wonder-Piggy, Batman and Zatanna confront Circe. They convince her to give them an audience when Zatanna smashes her with a piano. For Circe to change Diana back, Batman has to bare his soul in front of an audience, singing "Am I Blue?" to Circe's nightclub patrons. Zatanna admits he has a lovely voice, and Circe reverses the spell just as Wonder-Piggy is about to end up sliced in a slaughterhouse. Diana thanks Batman for saving her; when he claims to not know what she's talking about, Diana walks off humming "Am I Blue?" cheerfully. Batman can't help but smirk.
 * Over the Garden Wall has a moment of this save the main characters. They hopped on a frog ferry without paying the fee, because Greg tossed the pennies away impulsively, so they have to disguise themselves as band members to hide from security. When Greg and Wirt accidentally knock out the bassoon player, Greg encourages Wirt to play. Beatrice the bluebird does as well, because she suddenly doesn't want them to go see Adelaide. Wirt picks up the bassoon and plays...and Greg's new frog suddenly belts a beautiful melody. The frogs sing along, and they allow the humans to stay on the boat as long as Wirt keeps playing. They even offer Greg's frog a musical contract, but he chooses to stay with the trio.

Other Media

 * At some sports games, football fans may have a song that inspires the crowd to chant. For the Miami Hurricanes, as one example, they sing a riff from the White Stripes song "Seven Nation Army" as a game is starting.
 * Similarly, soccer fans in Europe have for some reason seized on the theme song to the 1969 Pippi Longstocking TV series as a crowd chant.

Real Life

 * This is why it is always a pleasure to see random flash mobs, musical buskers, and dance-offs in public. People will always be tapping to a beat and willing to sing.
 * You never know when two Broadway troupes will appear at the same time in an airport, and have a sing-off. Such as when the Broadway casts of Aladdin and The Lion King happen to be waiting for flights.
 * At BigFest Con in 2016, a band performed the Gravity Falls theme song for Alex Hirsch. He was so overjoyed, he joined their square and started dancing along.