Road trips are so much groovier in an iPod/XM/CD-burning/file-sharing era that makes the golden age of mix tapes sound like really old news.

Yet 75 years ago, all you could hear in a car was chatter and clatter. If you wanted music, you sang as you drove. Your friends and family should thank Elmer Wavering, William Lear and Paul Galvin for sparing their ears from your voice.

In 1929, Wavering and Lear drove their girlfriends to catch a sunset from a scenic parking spot on a high bluff overlooking Quincy, Ill. The women suggested it would be really cool to have music in the car, and the two tech-minded radio tinkerers thought that sounded like a pretty neat idea. Their main challenge was eliminating assorted sources of interference from the car's engine and electrical system that might drown out the music. Soon after, Lear met fellow tinkerer and fledgling radio manufacturer Galvin at a Chicago radio convention, and he invited Lear and Wavering to build a radio from scratch and install it in his Studebaker sedan.

Some quick context-heavy history: Commercial radio broadcasting began in 1920 at KDKA in Pittsburgh, an hour a night at a time when there were only 3,000 radio sets in the entire country; two years later, there were 300,000 and by 1930, 2.5 million. In the '20s, Henry Ford introduced the mass-produced automobile, and in 1926, radios were first introduced in cars -- portable, battery-driven "travel radios." A year later, a breakthrough came with the invention of damp resistance, making it possible to listen to a radio when the engine was running -- at least when the car was near a transmitter. Some folks had radios installed on a custom basis, but that was quite the luxury at $250 a pop (the equivalent of $2,845 today).

Not surprisingly the market was pretty small, but Wavering, Lear and Galvin thought that by mass-producing car radios, and thus lowering the price, they could create a large new market, a good, albeit daring, idea in the wake of the 1929 stock market crash and ensuing Depression. Literally test-driving his sonically souped-up Studebaker over 795 rough-hewn miles of roads and highways, Galvin arrived at the June 1930 Radio Manufacturers Association convention in Atlantic City. Unable to afford a booth at the show, he parked outside the front door and (thanks to a speaker Wavering had installed under the hood) cranked up his radio to capture the attention of convention-goers as they walked from their cars to the exhibition hall.

By the end of the convention, Galvin had received a few orders for the 5T71 car radio, which cost $110 and which owners installed themselves. For the year, sales totaled $287,000, with a loss of $3,745. It would be the only loss suffered by the company, which soon changed its name from Galvin Manufacturing Corp. to Motorola, a new word taken from "motor" and "Victrola" to suggest sound in motion. Motorola would dominate the market for car radios for years to come, particularly after 1933, when Ford began offering preinstalled radios in its lines.

Wavering and Lear soon split with Galvin but would continue to play a major role in your car comfort and listening pleasure. Wavering invented the alternator, which made it possible for cars to use an electric ignition and air conditioning, while Lear (yes, the one behind Learjet, the world's first cheap, fast, mass-produced business jet) invented the eight-track cartridge tape system.

In 1956, Ford had helped develop a four-track, shell-encased continuous-loop audiotape system as a means to give drivers the option of listening to music of their choice while in transit, but problems in jamming, accessibility, tape time and sturdiness made it pretty much unmarketable. Lear improved the existing four-track, doubling the potential playing time and increasing accessibility to individual selections. And like Galvin, he struck a marketing deal with Ford, which in 1966 began offering factory-installed in-dash eight-track players in all its cars. (A year later, Chrysler and GM did the same.) Originally, both four-track and eight-track prerecorded tapes were sold only in auto parts stores and truck stops. But it was eight-track that would be the first tape format to achieve mass-market success, becoming the preeminent car audio format through the 1970s and paving the way for all sorts of innovations in portable listening.

Then in 1963, Phillips introduced the cassette tape at the Berlin Radio Show. Cheap, durable and portable, it was seen by the record industry as exactly the same piracy threat that downloading is today. On the positive side, like downloading, the blank cassette allowed music lovers to become their own DJs while creating customized, highly personal compilations for friends, family and lovers -- and for long road trips. In his new book, "Mix Tape: The Art of Cassette Culture" (Universe, 2005), Sonic Youth's Thurston Moore talks to more than 80 "home tapers" -- musicians, artists, writers, actors, directors and record store clerks -- about the stories behind their labor-intensive mixes. Cool stuff.

Sadly, like eight-tracks from the '70s, mix tapes are pretty much a thing of the past in the new age of CD burning and downloading (according to the Recording Industry Association of America, audio cassettes accounted for less than 0.2 percent of music sales last year), so the Moore-edited anthology -- which includes reproductions of mix-tape inlays and track lists -- is as much an elegy as the 1995 documentary "So Wrong They're Right," about "trackers," the underground network of eight-track tape collectors.

In other words, keep those iPod track lists and such handy. There's a book in their future as well.

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A diagram circa 1930 details the installation of a Motorola car radio, which was once a luxury.