By Darren Waters
Technology editor, BBC News website
The growth in online music is about much more than simply downloading songs - it is also about changing the way people listen to music and what music they listen to.
Online radio stations are like a never-ending jukebox
Last night my computer played a song I had never heard before and I loved it. It then played another, and another, and I loved them both.
The music was being played through a free web service called Pandora. It created a personalised, online radio station for me based on a single song I had told Pandora I liked.
From that point I was able to give the thumbs up or down to each song it played me, building up a profile of my listening tastes.
Tim Westergren, the chief executive and one of the co-founders of Pandora, said: "We try and create something of a musical journey within the context of a song, band or artist you have given us."
Pandora works by associating different songs, artists and bands together based on a series of musical attributes.
But there is not a computer algorithm in the background analysing music, the work is done by a 42-strong team of musicians.
"They listen to each song individually and analyse it along 400 musical attributes," said Mr Westergren.
"It can take as long as 30 minutes to do a single song," he said.
"A musician has listened to that song and captured hundreds of little details about it which are literally scored on the song.
"We have a big template which you can think of as a music genome or music DNA. We compare that to every song in our catalogue.
"There is a fairly complicated math equation which takes that musical information and calculates what song is closest to it."
The whole service works within a web browser - there are no downloads or programs to install.
There are other similar services available online, such as Last.FM and LaunchCast and ShoutCast, reflecting a growing trend of music based around personal choice and networks of like-minded people.
Pandora has 2.5m registered users and Mr Westergren said the service could support hundreds of thousands of people listening to their personal radio stations simultaneously.
The music is streamed to your computer at 128kbps - roughly the quality of a music download - and is never actually stored on your machine.
Pandora lets you give the thumbs up or down to songs
There are links to online music stores such as Amazon and iTunes if you want to actually download the song you have listened to.
Pandora started life seven years as a project to help people find new music and has existed in its current form for just eight months.
Mr Westergren said: "We launched it from a one-bedroom apartment in San Francisco. It's a typical start-up story
"There was the simple intention of creating some new way of discovering music."
Pandora has more than 500,000 songs in its catalogue and new tracks recommended by users and discovered by staff are being added each day.
Record labels have also taken notice and are sending music to Pandora every day.
"We also get a lot of submissions directly now from musicians, bands and labels. That means everything from majors to people doing stuff in garages.
"We want it all. We don't discriminate or prioritise because music is on a label or not.
We do have to have the mainstream as typically that is what people use to launch a station."
But should users be suspicious if a song from a major artist pops up in their playlist?
"We will never ever play a song on Pandora because someone has paid us to play it," said Mr Westergren.
Pandora can create up to 100 different radio stations and each station can be made more varied and diverse by adding more favourite artists or songs.
At the moment the service is limited to US owners because of restrictions over streaming websites.
In the US Pandora has a one-size-fits-all licence which covers streaming copyright music but the company has to negotiate with individual record labels in the UK and the rest of Europe.
Non-US residents can use Pandora simply by entering an America zip code during the registration process.
"Pandora's success so far has really smoothed the way for us to get that done," said Mr Westergren, adding that Pandora should launch in the UK soon.
The company is also looking to offer Pandora as part of the digital home and mobile listening.
At the moment users of the Squeezebox wi-fi music device can listen to the station via their hi-fi and there are other solutions involving downloading third party programs.
Mr Westergren said: "We really would like to make this an anytime anywhere experience. The home networking world right now is a bunch of small companies - Sonos, Roku and Slim Devices.
"It's a matter of time before Sony or one of these big companies gets into that space and that's when it will take off.
"We would certainly like Pandora to be available to all those devices and make it available on mobiles or some kind of wi-fi MP3 player."