Tim Williams and his twin brother, Fred, recently recorded themselves listening to the nearly 40-year-old hit “In the Air Tonight” by Phil Collins. In the video, the two ride the ebb and flow with some serious head nodding as the song swells toward a climactic moment.

“Hold on, I didn’t prepare for this. I have to prepare,” Tim Williams says, with the song paused, as he pantomimes putting a seatbelt on.

When they hear the pounding drum break, their bodies slam back in their black leather computer chairs and they look at each other in shock.

“That was cold!” Fred Williams says. “I ain’t ever see nobody drop a beat three minutes in a song!” The video reverberated around the internet and accumulated more than five million views and counting on their YouTube channel.

The Gary, Ind., twins have also recorded their first time listening to Whitney Houston’s “I Will Always Love You,” Janis Joplin’s “Piece of My Heart,” and Dolly Parton’s “Jolene,” which she responded to on Twitter. “No point in begging…Jolene already stole these two,” Ms. Parton said.

The Williamses began to record their reactions to songs they had never heard last year, but reaction videos to music, whether on YouTube or TikTok, have recently gained in popularity.

Some show people reacting to genres of music unfamiliar to them. In other videos, older people react to more modern songs. On TikTok, the amusement is focused on which well-known songs from the last decade that teenagers do or don’t know. Sometimes the reactions are faked, but the Williams twins say theirs are honest.

Whether you learned about oldies while in the back seat of your parents car, hunched over the family computer scouring the internet for the origin of a sample, or while recording your reactions for YouTube, music discovery can be a joyful experience.

In the past, it was easier to learn about pop classics from parents, record stores or radio stations. But today, streaming music algorithms are designed to keep the listener under a spell in a bubble of the music they prefer. Discovering a golden oldie has become increasingly harder to do.

“The algorithm is built around user behavior,” Ebro Darden, the global head of hip-hop and R&B at Apple Music, said. “As more consumption options became available for music lovers, platforms got narrower and more targeted.”

Discovering classic jams on the airwaves seems hard to do now, too, as radio stations have also become more personalized, Mr. Darden said.

“You are beholden to a platform, whether it is a radio station or a streaming service, whether it is a human curation or an algorithmic curation, but you can go into these services and start looking around,” said Mr. Darden, who also hosts Ebro in the Morning at the New York radio station, Hot 97.

On streaming services like Apple Music or Spotify, users can decide if they want to go down a rabbit hole and listen to music based on the era, genre, producer, or artist, but they have to take the first step, which seems to be a hurdle.

Many users want their music tailored to their taste by someone else, according to Ray Heigemeir, the public services librarian for music at the Stanford Music Library.

“People will have to do a little digging,” Mr. Heigemeir said. “Today, people want to pick something and have it done for them.”

Most streaming services curate playlists where users can discover new music. Spotify uses their “Fresh Finds” playlist to get new music to their customers. The platform also offers thousands of playlists based on different factors, from era to genre, to appeal to all listeners, said Lizzy Szabo, a Spotify playlist editor.“The more you use the app the more personalized the app becomes for you,” she said. “The personalization is trying to serve you things you might have a connection with but it takes the effort of the listener to decide what they want out of Spotify.”

The decline of record stores and the rise of themed radio stations may make it hard for music lovers to find new songs to tap their feet to. Many feel overwhelmed by the vastness of music itself and stick to what they are accustomed to. So perhaps it’s no wonder that aspiring DJs on YouTube and other platforms have found an audience for “first time we heard” videos.

Music has always been vast, according to Mr. Darden, who has worked in radio stations across the country since the 1990s.

“Hard working regular everyday people are looking for someone that they can trust the most for a sound or a genre,” Mr. Darden said. “People like D.J.’s because you want to listen to a trusted content source.”

On YouTube, the Williams twins take audience suggestions in the comments about which songs to listen to next. You can watch them thrill to Janis Joplin singing “Piece of My Heart,” Jimi Hendrix’s “Hey Joe,” and other hits from performers and bands that used to top the charts, like Elton John, John Lennon, Led Zeppelin, Supertramp, Nirvana and Heart. (“I think it’s a band or a group, I think so, made in 1977,” Tim says as “Barracuda” begins. “It’s a girl act?”)

Christopher Washburne, a Grammy-award-winning professor of music at Columbia University, likens the duo to a modern version of a fanzine.

“They are turning on their peers to music of their parents’ generation and showing them how and what to appreciate,” Dr. Washburne said. “They are emotional guides giving us instruction and how to feel.”

The twins, who are fans of rap and hip-hop, are also getting history lessons about their favorite genres, according to Dr. Washburne. “They are actually listening to the roots and history of their own music because many of the songs that they listen to are sampled in hip-hop songs,” he added.

“The white artists they listen to are often performing music co-opted by white people,” Dr. Washburne said. “In some ways, what they are doing is co-opting the music right back.”