Three aspects of Internet radio
The term "Internet radio" seems to be everywhere. Internet radio's now built into an increasing number of smart phones, laptops, TV, streamers and even tabletop radios. But what exactly is "Internet radio?" If you're one of Pandora's 50 million registered users, or one of the 42 million listening to a web-only show through SHOUTcast, then you're listening a form of Internet radio.
Without some sort of definition, though, it's difficult to see all the exciting possibilities this new medium offers.
Internet radio as streaming audio
At its most basic level, "Internet radio" simply refers to audio streamed online. Many people are familiar with the concept of downloading audio tracks and storing them on a computer, which is similar to purchasing a recording at a store. By contrast, streaming audio is more like traditional radio — while the sound plays through your computer (or other Internet-connected device), it isn't permanently stored on it. Information is continually downloaded, played, and discarded, flowing past like, well, like a stream.
Part of the reason the term "Internet Radio" caught own was because the transient nature of an audio stream is analogous to that of a terrestrial radio signal.
Three basic types of audio streams share the moniker of "Internet radio;" simulcast signals, webcasting, and interactive audio streams.
Simulcasting — over the air and over the web
The term "simulcasting" is a shortening of the phrase "simultaneous broadcasting." This is the simplest form of audio streaming. A terrestrial radio station simply feeds its signal both to a transmitter for over-the-air broadcast and into a server for online distribution. For many broadcasters, this is the extent of their Internet presence.
An online simulcast can be a great way to listen to radio stations outside your coverage area - even outside your country. Most radio stations that simulcast will have links to their Internet feed on their station website.
Webcasting — music chosen for you
Webcasting, in some cases, is only one step removed from simulcasting. Some terrestrial radio stations (mostly public broadcasters) set up a secondary channel for content different than their over-the-air programming. Sometimes this content is also simulcast on an HD2 channel, but often it's only available online. This type of content, like a simulcast, sounds very much like traditional radio programming with announcers and spot breaks.
Independent webcasters also make up this second group. Most of these Internet-only webcasts feature highly specialized programming created for very small niche audiences. Unlike feed originating from over-the-air broadcasters, these type of webcasts are extremely music-intensive and often have no announcers, although some may have occasional identifiers, and perhaps some advertising.
Interactive audio streams — music chosen by you
The third type of streaming audio features some element of interactivity. This includes services such as Pandora, Last.fm, and Slacker. These services allow you to set up your own "radio station." You generally start with a core selection of songs and/or artists. The service then selects a song based on the criteria determined by your choices. As the song plays, you decide if it fits your station or not. That decision influences the next song the service selects. The more you use your "station," the better the service gets at making selections based on your aggregate choices.
Like the other forms of streaming audio, though, there is an element of uncertainty. You can't preview upcoming selections. Just like (in theory) with over-the-air radio and other kind of audio streams, you don't know what's coming up next until it starts playing. And like with other types of audio streams, once you break the connection, nothing is saved to your device's memory.
Paying to play — all yours for a price
While the vast majority of audio streams collectively known as "Internet radio" are free, there are some that are only available to paid subscribers. The good news is that almost all of these services have some sort of free trial listening period, so you can try them out first.
SIRIUS/XM Satellite Radio like terrestrial radio stations, streams — or simulcasts — its programming online. But only subscribers can receive these feeds.
Rhapsody combines the niche programming of webcasting with the interactivity of Pandora and Slacker. Your paid subscription gives you access to the all the genre radio stations Rhapsody offers. You also can choose your own music from Rhapsody's library, and download it to your player to listen to later.
Some services also offer two tiers of service — free and paid. The free versions of Pandora, Slacker, and Last.fm are ad-supported, and have limited options. Their premium services offer ad-free music streams, and additional features and benefits.
So what's the point?
As Jim pointed out in a previous post, the biggest appeal for what's known collectively as Internet radio is the opportunity for discovery. Stations all over the world are simulcasting, so you can find out what people in other countries are listening to. Webcasters let you dig deeper into your favorite genres, uncovering music and artists you might not find otherwise. And interactive services can surprise you by serving up songs that fit into the mix you've created, but you might never have selected on your own.
So while "Internet radio" may refer to different types of online audio streaming, in a sense it all refers to one concept — audio adventure.