These days, even small, inexpensive cars such as the Fiat 500 and Kia Soul can be bought with high-end stereo systems from prestigious brands such as Beats by Dr. Dre and Infinity.

But why can't today's music match the sound of that old-time rock 'n' roll?

It's not the speakers. It's the format.

No matter how advanced the stereo system, it can't do much to improve the low-fidelity sound pouring out of MP3s and streaming Internet radio services such as Pandora and Spotify, says Jeff Poggi, vice president of global sales and marketing at Harman International Industries, which sells speakers under brands such as Harman Kardon.

"All the new media is at a lower fidelity level than the CD was," Poggi says. "That's really the fundamental challenge that the industry is up against right now."

It's fundamental because the sound of music is money. Automakers long have used premium audio offerings, such as branded stereo systems, to sweeten trim packages. Porsche, for instance, charges $2,120 for a Bose stereo in its iconic 911. Buyers of Mercedes-Benz's flagship S-class sedan can now pay $6,400 for a top-of-the-line Burmester sound system. And much of that amplifies the bottom line.

"Out of all of the options you can add into a car, premium audio has the largest profit margin for an automaker," says Mark Boyadjis, a senior analyst at IHS Automotive. "There's not always a lot of cost involved in creating a premium audio system."

But customers who prefer the convenience of low-fidelity formats gain little from such systems. So Harman is trying to meet customers where they are.

Harman's solution is a software algorithm, originally dubbed Signal Doctor and now branded as Clari-Fi, that analyzes music files and restores what was cut when the file was compressed. The system will make its debut in the 2015 Lexus NX compact crossover, Harman announced in April.