Broadly, automakers are divided into two camps. The first includes those who’ve drawn inspiration from the sound of gasoline cars—or at least tried to make it sound as if something is at work under the hood, though often with a futuristic edge. Audi falls into this category, as does Ford, where sound engineers tried to make the Mustang Mach-E sound reminiscent of its gasoline-powered namesake. “It has to have a perception of power, a perception of grit,” says Ford sound-design engineer Brian Schabel. Engineers at British automaker Jaguar took a similar route, paring down the essence of a rumbling V-8 engine and high-revving motorbikes for its I-PACE electric crossover. “You want to get right to the good state where people are comfortable with it, they can understand it, and it’s not too weird,” says Jaguar Land Rover sound engineer Iain Suffield. Audi sound engineer Stephan Gsell agrees. “The vehicle is a technical device,” he says. “It’s not a musical instrument.”

On the other side are carmakers that have little interest in replicating the sound of a gasoline engine at all. “We shouldn’t be trying to communicate that there are moving pistons in this thing,” says Danni Venne, lead producer and director of innovation at Made Music Studio, an audio branding agency that designed the engine sound for a recent iteration of the Nissan LEAF. “We’re somewhere else now technologically.” The LEAF sound, Venne says, has “a little bit of a singing quality to it.” GM also took a step in the musical direction, creating EV sounds using sampled guitar, piano and didgeridoo. “We want it to sound organic, yet futuristic,” says GM sound engineer Jigar Kapadia.

Then there’s whatever BMW is doing with its i4 electric-sedan concept. At low speeds, the i4 sounds like an electrified orchestra warming up for a performance. But as it accelerates, the tone becomes deeper and lower. Then comes a high-pitched skittering effect, as if some kind of reality-bending reaction were taking place under the hood. “We conceived a sound to celebrate the car, intended as a highly complex performative art installation,” says BMW sound designer Renzo Vitale. Vitale, who worked alongside famed film-score composer Hans Zimmer on the i4, says it was his counterintuitive idea to make the noise deepen as the car gains speed. “It was a metaphoric way to say, ‘We are looking at the past,'” he says. Given Vitale’s curriculum vitae, it’s not surprising BMW ended up with an unconventional result: he composes electronic and orchestral music in his free time, used to play in progressive metal bands and, while getting his Ph.D. in acoustics at Germany’s RWTH Aachen University, created bold live performance art. “I was performing naked, painted black in crazy installations,” Vitale says.

While sound designers like Vitale are excited about the artistic potential in EV sound design, automakers are salivating over the marketing opportunities. One highly produced promotional video posted online by Audi dramatizes its engineers’ search for the perfect sound, featuring the team pensively observing helicopters and wind tunnels. Ford worked with a musician to produce an EDM track sampling the Mach-E’s engine tone. Zimmer features heavily in a recent BMW promo video advertising his work on the i4. “Sound underlines the soul of anything,” the composer says in the spot. “Right now, we are at a really exciting point, shaping the sound of the future.”

Courtesy Audi

All this marketing and branding exuberance may die down if car buyers embrace vehicles that are simply quieter rather than noisy in a different way; EV engine tones may eventually be pared down to only the simplest, most essential sounds. Some experts think carmakers will start using retro gasoline-engine sounds in EVs. Others suggest they will include systems that enable drivers to customize their cars’ engine noises, to make them sound like anything from a motorboat to a spaceship. (Tesla CEO Elon Musk is particularly fond of similar gimmicks; Wikipedia’s “List of Easter eggs in Tesla products” includes more than two dozen examples.)

That last scenario alarms Trevor Cox, a professor of acoustic engineering at the University of Salford in the U.K. and author of The Sound Book: The Science of the Sonic Wonders of the World. “The submotive sound of every city is pretty much its cars,” says Cox. “As soon as you change the sound of cars, you’re going to change how the city sounds.” He argues that excessive customization and diversity of vehicle sound could turn urban soundscapes into jarring, chaotic disasters. “We have a sense of what hell would be like, because we lived through it when people first got mobile phones,” he says. “[Everyone] decided to have a ringtone that was individual, and you had this horrible cacophony.”

But plenty of people leave their smartphones in vibrate-only mode, and it’s likely that most EVs will end up being quiet compared with the gas-powered models we’re used to. That could have major benefits for city dwellers in particular, as studies show that constant exposure to traffic noise can increase people’s risk for high blood pressure, heart attack and stroke. Combined with their lack of emissions, EVs’ relative silence could even make it less awful to live near a major road, fundamentally changing urban design. For that to happen, some sound experts say automakers need to remember that what sounds innovative and interesting in a studio might inspire quite a different feeling for people out in the real world. “We need to have some self-imposed guardrails,” says Pierce. “Not only to do right by our customers but to worry about the society as a whole.”

Driving around New York City in Ford’s Mach-E, I thought about what the roads of the future might sound like. The not-quite-Mustang produced a humming, vaguely electric noise as it accelerated, halfway between a pony car and a Star Wars pod racer. Several EV sound designers spoke about being inspired by sci-fi movies; Zimmer himself composed the score for Christopher Nolan’s Interstellar. Those films may have created a kind of self-fulfilling prophecy, as our imagined futures shape the real sounds of our streets. While sci-fi movies tend to be dystopian, these designers’ work may end up making our future cities at least a little safer and healthier, with less sound and air pollution. But exactly what our streets will sound like when they’re crowded with EVs is still in the hands of those auditory specialists with their strings and synths. “Hans and I keep talking about elegance, the idea of bringing elegance to the streets,” says Vitale. “We want to share a vision of the sound of the future that maybe helps make cities a better place.”

Correction, April 8

The original version of this story misstated Ford’s investment in EVs. The company is investing $22 billion, not $11 billion.

This appears in the April 12, 2021 issue of TIME.