Today, the songs of humpbacks are famous. They fill the halls of spas and they’ve been satirized by Pixar. But fifty years ago, they were largely unknown. That changed in 1968, when scientist Katy Payne and her then-husband Roger took a trip to Bermuda and met a Navy engineer who had been inadvertently recording the whales. “Tears flowed from our cheeks,” Payne later told NPR about the first time she heard the recordings. “We were just completely transfixed and amazed because the sounds are so beautiful, so powerful—so variable.”

The Paynes showed that the calls have a structure that strongly resembles human songs, that they change dramatically and irreversibly over time, and that they even contain repeated elements akin to human rhymes. Roger also released some of his own recordings in an album that became a surprising smash-hit, helping to spark the Save the Whales movement and ultimately leading to a ban on whaling.

It’s only male humpbacks who sing, and they only do so during the breeding season. “We aren’t sure whether it is for attracting mates or repelling rivals but it has something to do with mating,” says Ellen Garland. The songs are hierarchical. Single sounds—units—are grouped into phrases, which are repeated to form themes, which are delivered in a specific order to create a song.

At any given time, all the males in a population sing the same song, but those songs also change. Like jazz musicians, males riff off the classics, making small tweaks as they go. And occasionally, they throw the current song out the window and take up a completely new one—revolution, rather than mere evolution. “We think that the males change their songs to be a bit different to other whales around them, and be more attractive to the ladies,” says Garland. “This is then reeled in by the need to conform, which is the same as with humans. In our society, when a new fashion appears, a few savvy people embrace it and everyone else quickly follows.”

In 2011, Garland and Noad showed that these revolutions take place very quickly, and across entire oceans. Like “cultural ripples,” songs that arise in one end of the Pacific can spread to the other within a few years, “This is incredibly quick,” says Garland, “as whales need to learn all the intricacies of the new song.”

To understand more about how this process happens, Garland and her team analyzed recordings that caught humpbacks in the act of switching songs. These mash-ups, where the whales were blending both old and new melodies, were so rare that the team had only recorded five in over 20 years of fieldwork—and one was too poor in quality to use.

Still, the other four hybrids revealed a clear pattern: The humpbacks were combining themes from both old and new songs, but leaving each individual theme largely untouched. Sometimes, they sang a transitional phrase to bridge the gap between the two segments. Sometimes, they melded one song into another at places that were musically similar, like the world’s largest deejays.