Some of the most beautiful and beguiling sounds in the natural world are made by singing animals.
Beautiful due to quality and range of the sounds, and beguiling due to their complexity and the complicated reasons animals sing them.
And perhaps no singing animals have fascinated us more than the great whales.
Bowhead whales are unique among all other whales in that they change their songs within and between years
The songs of humpback or blue whales remain the most well known, but new research is helping to confirm that an even more impressive songster swims, and sings among them.
The bowhead whale has the most impressive repertoire of all whales, and scientists have just recorded 12 unique songs being sung by bowhead whales on their annual migration.
The discovery reveals more about how these enigmatic creatures, which spend much of their lives swimming under thick Arctic sea ice, communicate.
The new research focused on one population of bowhead whales on their annual spring migration along along the west coast of Alaska.
The researchers recorded more unique songs (listen below) during this period of migration than has ever been observed before in this group, which belong to the Bering-Chukchi-Beaufort population, the biggest of four geographically isolated populations.
The study, published in the journal Marine Mammal Science, also found that at least six of these songs were shared among travelling members of the group.
Using underwater microphones called hydrophones, the team recorded songs at two locations and found 12 unique songs (listen below) from 32 individuals.
A previous study recorded a greater number of 66 unique songs, but over a much longer period of one year.
While other species such as the humpback, sperm, and blue whale also sing, it is the bowhead that appears to have the greatest number and diversity of songs.
Such insights have come only recently, as the remote Arctic habitat of the bowhead whale, covered with thick sea ice through much of the year, makes them extremely difficult to observe.
These whales are also known to vary their tunes from year to year, but just how many songs they have in their repertoire, or why they exhibit this behaviour at all remains unclear.
This is exactly what co-author of the new research, Kate Stafford of the University of Washington in Seattle, US, hopes to uncover.
Bowhead whale songs are thought to be social calls or some sort of a reproductive fitness display. What's clear is that whales can learn these songs from each other.
"Bowhead whales are unique among all other whales in that they change their songs within and between years," Stafford told BBC Earth.
"It would be really great to understand not only why they sing but why they sing so many different songs."
That they are so different intrigues Stafford. The four known bowhead whale populations, for example, have never been observed singing the same songs, though she cautioned that it was still a relatively new field of research.
"Of all the baleen whales, humpback are the best known singers, everyone's heard about the haunting song of the humpback whale, but every one of them will sing the same song every year. When the song changes the rest adopt the new song," she said.
Listening under the ice, you're always going to hear and discover something new
"It's fascinating that the bowhead whale should be so different from other species of whale."
The variety of their verse could, in part, be attributed to their now rapidly increasing numbers, a promising tale for a group which were once almost brought to the brink of extinction by whalers in the 1600-1800s.
Now that it's possible to leave hydrophones under the water for over a year, researchers aim to eavesdrop on many more of their mesmerising songs.
"Listening under the ice, you're always going to hear and discover something new. We think of the arctic as this potentially vast frozen wasteland. It's not, there is so much going on all year round under the ice, and it's this magical, magical world," said Stafford.
"If I could spend the rest of my career listening to bowhead whales with a hydrophone, I'd be a happy person."
Follow Melissa Hogenboom and BBC Earth on twitter.