If you're an average American commuter, you spend more then an hour behind the wheel every workday. During drive time, your car stereo is the only thing standing between you and total insanity. Fortunately, the digital revolution brings you more choices than you can imagine - whether your tastes run to Beethoven or Beyonc?, Mike and the Mad Dog or Morning Edition, or the latest thriller by John Grisham.

So, lend an ear to what's hot in car audio - and viva la revolucion.

Digital Downloads

Personalization and portability have made Apple's iPod the iconic audio product of the 21st century so far. A recent survey by J.D. Power and Associates found that more than half of U.S. consumers want to play their digital music files in their next car, and 60 percent of iPod owners are willing to pay $150 to connect their iPod to their cars' audio system.

After a slow start, automakers have finally begun to integrate iPods and other personal digital music devices into their sound systems - eliminating the need to hassle with an FM modulator or suffer the degradation in sound quality with a cassette adapter.

BMW took the lead two years ago, becoming the first automaker to offer a glovebox adapter to let you hard-wire an iPod directly into the car's stereo system and control it through buttons on the dash. Since then, Acura, Audi, Ford, General Motors, Honda, Mazda, Mercedes, Nissan, Subaru and Volkswagen have introduced similar interfaces. Apple estimates you can get iPod integration on 70 percent of 2007 models.

But suppose you don't want to buy a new car just to play your iPod. For about $100 (plus installation),you can probably buy an aftermarket adapter that lets you play your personal digital music collection through your vehicle's factory-installed stereo system. If you've upgraded your stereo with an aftermarket system, you can almost definitely find a compatible iPod adapter.

MP3/WMA devotees have other options. Many CD players on newer cars include a chip that enables you to play digital music files stored on CD-R/RW discs. And more and more stereos now come with USB ports that let you plug in a thumb drive or memory stick and play stored tunes. On the aftermarket, prices for such units range from $120 for Best Buy's model to $300 for units from prestigious brands such as Clarion, JVC and Kenwood.

"New" Old Media

Sick of shuffling CDs, but still not ready for an iPod or MP3 player? Certain Infiniti, Jeep, Lexus, Mitsubishi and Nissan models offer navigation systems with plenty of hard-disk space to spare, letting you record music from CDs and other sources directly onto the in-dash system.

In the 2007 Lexus LS 460,for example, the navigation system's hard drive can store up to 2,000 songs, but only from ordinary audio CDs. And DaimlerChrysler's "MyGIG" entertainment/navigation device- which will be made available in the Chrysler Sebring, Jeep Wrangler and Dodge Nitro's 2007 models-can download some 1,600 songs from CDs in the music player or USB devices plugged into the radio. Of course, these carmakers bundle the feature with their navigation systems, which list for as much as $2,000-making CD-less convenience mighty pricey.

Book lovers who want to dump CDs have a better option. Tiny Playaway devices deliver the spoken word (and, increasingly, music) in a pre-loaded, virtually idiot-proof player-plus storage device. About the size of a pack of Tic Tacs, each Playaway has up to 40 hours of digital audio content. You can listen on your car stereo with a standard cassette adapter or FM modulator, or with headphones when you're not driving. Because you don't have to juggle five or six CDs or a dozen cassettes to get through a big book, Playaway represents a safer, less distracting alternative for behind-the-wheel listening. And since they use flash memory, they can't scratch like a CD or bake in a hot car like a cassette tape. You can find them at big-chain booksellers and at 300 library systems across the country, including the New York Public Library. The only problem - borrowers snatch them up the second they hit the shelves.

Despite the booming popularity of iPods and other digital storage devices, however, 75 percent of American drivers still rank radio as their No. 1 listening choice-way ahead of even CDs. And this enormous behind-the-wheel market is driving huge changes in both the delivery and content of radio. Here's what you can find now-and what's on the horizon:

Satellite Radio

What it does: Brings you at least 120 stations, mostly commercial-free, with music of all genres, news, talk, sports and entertainment.

Price: Base subscriptions run about $13 per month (plus activation fee); long-commitment plans lower the monthly price, and some premium channels cost extra. Hardware prices vary widely (see below).

How it works: Encrypted signals bounce off satellites and back to Earth, where your antenna picks them up and your specially enabled receiver decodes them. You get static-free reception, coast-to-coast. You can choose between two satellite providers-Sirius (with 4.7 million subscribers) or XM (with 7 million). Both offer music, news and information channels galore. In the high-stakes competition for ears, XM has enlisted Bob Dylan, Snoop Dogg and Tom Petty as celebrity DJs; Sirius boasts Howard Stern, Martha Stewart and 50 Cent.

More serious differences emerge when you consider sports, however. XM carries play-by-play for all Major League Baseball games, as well as ACC, Big Ten and Pac-10 football and basketball coverage. Sirius has play-by-play for the NFL, NBA and lots of big-time college games.

Both Sirius and XM feature local news, weather and traffic reports for the top 20 radio markets in the country. That's no problem in New York City, but elsewhere you have to rely on old-fashioned AM or FM for local content.

Some newer vehicles already come with satellite radio, and they usually include a trial subscription as part of the purchase price. Most automakers offer either XM or Sirius exclusively; only Infiniti, Lexus, Nissan, Porsche, Scion and Toyota give you a choice of satellite providers-at least, for now. In fact, the ranks of "pro-choice" automakers shrunk by two this year, as Audi and Volkswagen agreed to install Sirius exclusively through 2012. Otherwise you can upgrade your in-dash stereo to satellite ($50 and up), add satellite capability to your existing stereo ($50 and up) or buy a portable satellite radio ($180 and up) - a Walkman-size unit that you can use in your car, home, or anywhere else,just like an iPod or other portable radio. Some of these units let you play MP3/WMA files and include a memory buffer (so that you can pause a live broadcast and then resume listening, without missing anything).

Caveat: Even though the total number of satellite subscribers is expected to jump almost 25 percent this year alone, both XM and Sirius continue to lose money by the hundreds of millions, leading to industry whispers about a merger. Whether such a move would actually come to pass, whether the government would approve it or how it would affect subscribers and content is anybody's guess.

Hot tip: Both XM and Sirius stream many of their channels online. Just punch in a code,and you can get satellite radio on any desktop or laptop with a high-speed Internet connection-a huge plus for college kids whose parents subscribe.

HD Digital Radio

What it does: Receives digital signals from broadcasters, with better sound quality and more program variety than analog AM and FM.

Price: $200 (plus installation) and up for aftermarket receivers or adapters.

How it works: Simply put, the HD radio technology allows AM and FM stations to broadcast both digital and analog signals simultaneously. "The best analogy is the cell phone's switch from analog to digital," explains industry spokesperson Mike Geylin. "It doesn't increase reception distance, but it does dramatically improve sound quality and the amount of data that can be transmitted."

A geek could explain HD digital radio's sound quality in terms of higher frequency response, greater stereo separation and the ability to eliminate reflected signals. But all you really need to know is that it makes FM radio sound like a CD and AM sound like FM-no pops, hisses, static or fade. And that's not all. Because the technology allows broadcasters to bundle digital signals and employ a sliver of spectrum space on either side of their frequency, stations can multicast-that is, offer two or three program choices from the same spot on the dial. For example, WNYC-FM now broadcasts National Public Radio's All Things Considered during weekday afternoon drive-time, while WNYC2 (the station's digital side band) programs classical music during the same time slot. Currently, about 600 HD digital radio stations in 68 of the nation's top 100 markets multicast.

HD digital radio boasts two other big selling points. For one thing, it's free.You need to invest in a receiver, but you don't pay a subscription fee. For another, it's local. Unlike iRadio or satellite radio, HD digital stations can broadcast news, weather and traffic reports specific to their coverage area.

Only BMW now offers the technology as an extra-cost option-and only on some of its models-but expect other carmakers to make it available soon. Until then, plenty of aftermarket suppliers can outfit your car with HD digital.

Caveats: Not all stations have jumped at the opportunity to invest in HD digital technology. Currently, New York State has 61 HD digital stations, including 11 in the New York City market, 12 in Nassau/Suffolk County and most of the others in the Albany, Buffalo, Rochester and Syracuse areas. But some areas of the country have zero. And, with HD digital radio, you have to suffer through commercials - as you do with any other medium that relies on advertising revenue.

Hot tip: "HD digital radio essentially provides a data pipeline into the vehicle," says Geylin. Within a few years, that data may include stock quotes, real-time traffic reports or a "buy" button that automatically lets you order a song or advertised product.

iRadio

What it does: Delivers more than 500 commercial-free music and talk channels to your cell phone and plays them through your car stereo.

Price: At press time, Motorola had yet to set a subscription fee, but expect it to run $7 to $10 per month.

How it works: According to Motorola, iRadio combines old-fashioned broadcast radio's sense of discovery with satellite radio's variety and an iPod or MP3 player's personalization. "Radio is still the place where you hear great music for the first time and where you remember songs that you loved in the past," says Dave Ulmer, senior director of marketing at Motorola. "Unfortunately, commercial radio has taken a spiral path in recent years, with fewer choices and less variety. iRadio changes all that and puts it in a device that you carry with you everywhere you go - your cell phone." iRadio channels run the gamut from traditional blues to world beat and every niche in between.

To use the service, you need an iRadio-enabled cell phone, a Bluetooth adapter for your car stereo (or an iRadio-enabled home stereo), a computer and a broadband Internet connection. Every night, using a USB cable, you download up to seven channels of music or talk shows while you recharge your cell phone. You can also load your digital music collection, allowing you to switch channels from iRadio to your personal library. Most iRadioenabled phones hold about 10 hours of music; you can boost the total by adding more flash memory.

For all its high-tech capabilities, iRadio still functions as a cell phone. It automatically pauses to let you take an incoming call (or not, if you're driving), and then plays again precisely where you left off, without missing a beat. And, depending on the model, you can snap photos, send text messages, download videos and do all the other stuff that you've come to expect from a cell phone, besides have conversations.

Hear a cool song? Just press a button, and the iRadio captures the name of the artist, title and other information, so you can purchase it online later and add it to your collection. This summer, Motorola test-marketed iRadio in six cities and expects to launch it nationwide by the end of the year.

Caveats: Unlike broadcast or satellite radio, iRadio stations are basically podcasts-really long podcasts, but podcasts nonetheless. That means you won't get breaking news, current weather reports or the latest traffic updates.

Hot tip: Motorola has developed what it calls the Get Heard Network, where you and your garage band can reach a nationwide audience by uploading music, diaries, interviews and more. And, yes, musicians get webcasting royalties, and listeners can add songs to their wish lists for purchase later. Access to Get Heard is free for artists and part of the regular subscription for listener.