Update: LAUNCHcast now is an HTML
player... this changed around November 2001, when Launch.com
was acquired by Yahoo!
Now, how does LAUNCHcast work? Basically, it's an Internet radio station you can set up to play your taste of music by telling it what kind of music you like. You can set this up more or less globally, depending on how much time you'd like to spend.
The various items you can rate are:
Each of those items can be rated on a scale of 0 to 100 (percents?), or a newly introduced star scale. All items have their respective pages where they can be rated (except for subgenres, which I think is bad because you could better judge which genre and subgenre you may like if you could see what music's in there for you). Artists, albums and songs also can be rated as they come up in your player. But to start up, you have to pick at least some genres to rate, and some of your favorite artists. Or, alternatively, you could listen to some editorial stations and rate the music featured there.
Basically, the higher you rate an item, the more frequently it will play. For items containing much music (like artists and genres), the songs you get are determined by looking at what's popular with other users inside that genre - and, of course, what you've already rated.
There are some more things to note: If you rate an album, artist or song 90 or above, you are considered a fan of that item, with the result that you get songs recommended (rated highly) by other fans of the same item.
There are, however, some limitations to the algorithm, which prevent you from playing only one artist, for instance. Also, not all record labels allow their songs used this way, so you'll only hear songs by two or three of the five major labels on your personalized station (which labels were used changed over time). And no matter how many songs you rate, the system will play your favorites very often.
And there are some limits to listening. Currently, you may only use your customized station for free for 400 songs a month (including the ones you skip). To get more, you have to subscribe to Launchcast +, which is only available in the USA and Canada, and which also gets you ad-free listening, more editorial stations, better sound quality options, selectable moods which limit your station by genres, directly selectable influencers who provide you with songs you haven't rated yet, and more options.
Currently, LAUNCHcast is the only free service offering such a level of personalized radio stations. There are other services offering similar things, but all of them are either subscription services only or different in some other way:
MSN Music offers stations based on nearly every song, album, artist or genre they offer for their subscribers, but you can't personalize a station by your ratings. You can only launch a station based on one of the items.
There are similar concepts available on Launch too, basically, called Editorial stations covering one music genre, and artist fan stations playing music rated highly by fans of one specific artist. But the music you get on Launch's fan stations is rather widely spanned, while what you got on MSN Music when you launch a station based on an artist closely sounds like the music done by that artist. However, all you get for free on MSN is a choice of some editorial stations relevant to an artist or album you view.
Last.FM seems to be a rather new service which also lets you rate songs, though on a simpler scale, but they only indirectly affect what you're listening to. The system tries to find neighbors with a similar taste to yours and then plays songs liked by those, which leads to stations matching your taste not nearly as close to those of Launch. However, you can get a personal station playing only your favorites for a month if you donate to Last.FM.
RadioMOI allows you to create your own station (called "Show") there, by picking the songs you want to have on your show. However, you can't pick whole artists or genres, and you also can't tell the system how much you like a song, it can only be inside your station or not. Also, they're a subscription service only. Without subscribing, you can't listen to anything there.
RCS's iSelector allows you to launch stations who mainly are operated by terrestrial radio station owners and then tell the player to play each artist or song more or less, or ban it altogether. However, nearly all of their stations are subscription (and then you only get one station, not all of them) and only available in the USA, with the only exception being Blue Note Radio, which only plays music by Blue Note Records (basically, Jazz) and is available for free and worldwide.
Then there's Media Unbound offering a personalisation service, as part of which you can get a personalized radio station which starts by asking you some questions about music you like, and then giving you a set of playlists of about 100-150 songs each, which are constantly rotated, but still don't stay the same, because you can rate each song, and lowly rated songs get replaced by songs you're supposed to like more. The downside of this is that it probably only works for some broadband users and will skip horribly for most of the other ones (it does for me, at least). Also, you can't really select in advance which artists and songs you get, but you'll see them in your playlist.
A slightly different concept is done by chartradio.de (but you have to speak German in order to be able to fully enjoy this). They allow you to build stations based on three requested songs, which will give you a 20-song playlist consisting of similar songs (but not necessarily the three songs you chose). You can then delete any song you don't like, which will be replaced by another song (which you can't choose).
Last, but not least, the MusicMatch Jukebox offers multiple kinds of personalized stations if you download and install it first.
Besides their editorial stations, they feature era stations, where you get to hear music from a time span you select. Then there are "Artist match" stations where you input some artists and you get songs by these and similar artists. However, you can't select the songs there. Then, on the Station Mixer, you can mix around with the Editorial stations and select how much music you want to have mixed in from each (which basically is like rating genres in LAUNCHcast). Finally, there's "My Station" which plays music based on the MP3's and CD's you recently played in the player. If you sign up to Radio MX for a subscription fee, you get more personalization, like an Artist match for up to 25 artists (normally there are only 5), or a station based on a playlist.
The same feature (stations based on artists) now is also offered by Listen's Rhapsody.
And now, let's drink to the deceased stations. Yes, there were other services like Launchcast who fell by the wayside over time...
Radio Sonicnet (which started out as Imagine Radio) USED TO be another site where you could put together your station by rating your genres and artists on a scale of 0 to 5, which would influence their likelyhood of playing. However, there were no recommendations played (but at some time they did recommend similar artists based on the ratings of other users), and you couldn't select individual songs. Sonicnet discontinued these private stations in Fall 2001.
Echo.com offered a similar concept as Launchast allowing you to rate artists, albums and songs, however, genres could only be switched on and off. However, in my opinion the recommendations you got there were far more accurate to your tastes than on LAUNCHcast. Alas, they shut down their stations in March 2002.
MediAmazing allowed you to put together a station by checking the genres you like. However, you couldn't personalize it any more, and last they got subscription too... before they completely shut down in September 2002.
There also have been some changes to services still existing. Here are the most important ones:
iSelector used to offer some demo stations at the beginning in various music genres. The genres they had were pretty consistent and fine-grained in their music selection (you got to hear the best songs of each genre and to select some subchannels for each genre), but quickly after launch, they limited the demo accounts to only work for about 24 hours.
Launchcast wasn't always limited for free users... prior to March 2004, they let you listen to your customized stations as long as you wanted to (albeit without skipping and in low quality only after you reached your limit, which was introduced in May 2003). They didn't have a subscription service until early 2003, however, before their Yahoo! buyout, they offered some things that now are only found in Launchcast +, like moods and influencers. Also, they offered more extensive genre pages (featuring all albums in one genre), charts and other lists back then.
MSN offered their sounds-like stations for free at some time before introducing their subscription service.
Finally, RadioMoi wasn't a subscription service until January 15th, 2002, but rather a free ad-supported service.