To explain this phenomenon, the British natural historians Gerald Barrett-Hamilton and Martin Hinton claimed in a 1921 review that the singing was a pathological behavior resulting from inflammation in a mouse’s windpipe, like a cough or wheeze. They didn’t suppose that illness simply lowered these animals’ voices—the way a bad cold does in people—which might actually be what happened to Sidebotham’s extraordinary mouse.

In 1948, Wolfgang Schleidt, a zoology professor at the University of Vienna, was the first to show that all field mice vocalize in pitches too high for human ears to hear. About two decades later, Gillian Sales, a senior lecturer at King’s College London, who has devoted her career to studying rodent songs, used a tape recorder to listen to the songs by slowing them down to 1/20 normal speed. This had the effect of dropping the mouse’s register into the range of human hearing, but it also made the vocalizations sound a bit like the slow, repetitive glissando of a slide whistle.

Analyzing these songs was incredibly tedious, Sales says. It all had to be done manually. Just measuring the pitch and duration of a few notes could take ten minutes. As a result, even though the following decades saw fruitful research on why and how mice sing, there wasn’t much focus on the structure of the songs themselves, according to Sales. No one thought of mice as a potential way to model human speech.

The tide turned for mouse song in 1999, when a postdoctoral fellow at Harvard made a serendipitous discovery. Timothy Holy was looking for ways of identifying female-mouse sex pheromones, and he reasoned that pheromones in urine might cause males to make sounds. To him, the male’s high-pitched squeaks were simply good indicators of pheromones’ presence; he didn’t even think of them as songs.

To listen in while his mice sniffed at the urine swabs, Holy recorded their vocalizations then lowered the pitch without slowing down the tempo. To his astonishment, he heard music coming from these little furry faces.

“I noticed basically right away that these vocalizations were a lot more complicated than I had grown to expect based on the reading I had done on the literature,” says Holy, who’s now a neurobiology professor at Washington University, St. Louis. “I remember joking with my postdoc mentor at the time that maybe these were like birdsongs, basically.”

Although Holy’s pheromone experiment never panned out as he hoped, his rigorous characterization of mouse songs led to a seminal paper in 2005 in PLoS Biology. Other labs took notice, and mouse-song research exploded.

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Among the limited number of other mammals that communicate vocally—including humans, whales, elephants, dolphins, and bats—none are ideal for the laboratory. Mice, by contrast, are small, cheap, and easily genetically modified. Labs routinely delete or add genes to the mouse genome; many transgenic mice can even be ordered from a catalog.