By Jim Reed
Newsbeat technology reporter
At first glance, it's an eye-catching deal: as much music as you like, straight to your mobile, with no monthly subscription fee. Nokia and Sony Ericsson are about to start selling new handsets with unlimited downloads included in the purchase price and other phone makers are expected to follow suit.
Record companies are keen on the idea. They hope these new 'all you can eat' deals will stop people illegally downloading music for free. So how will these new services work? And what's the catch?
So what exactly does this Nokia deal mean?
It's called 'Comes with Music' and here's how it's going to work. You buy a special handset from Carphone Warehouse and pick your pay-as-you-go network operator.
The first phone available is the 5310 for £129.95, although other models will be available in the future.
For that cash, you get a year's unlimited access to five million tracks from the four major record labels and any independents that Nokia manages to sign up.
So how is this different from a subscription service like Napster?
With a service like Napster, you pay £14.99 a month. With 'Comes with Music' the subscription is included in the price of the handset so there are no monthly fees.
Plus, if you choose to end you subscription with Napster, you lose access to your music library.
With Nokia, you get to keep any music you have downloaded after the year ends. But if you want to get hold of new tracks, you are going to need to buy a new 'Comes with Music' mobile every year.
Are there any other catches then?
Afraid so. All your Nokia music comes with built-in copy protection. You can only listen on your mobile or a single personal computer but you cannot transfer tracks across to a separate device like an iPod or burn it to CD.
Also, Nokia hasn't yet managed to do a deal with operators like O2 and Vodafone to let you download songs directly to your phone.
That means, to begin with, you will have to copy the music to your computer first over a standard broadband connection and then sync up your phone from there.
In the future, other handsets will be able to download directly from the Nokia Music Store but data charges will apply.
What about other phone makers?
Nokia's big rival Sony Ericsson is planning a similar kind of service called 'PaynowPlus'.
It has already done a deal with network providers so users will be able to download tracks directly to their phones.
Companies like Vodafone and O2 are expected to subsidise the cost of the handset, making it free on some contracts but with a reduced number of minutes and texts.
Like the Nokia deal, music will be copy protected. But when the contract is up, users will be able to keep up to 300 most-played tracks in an open format which can be copied to another device.
Will this really stop people using dodgy websites to get their music for free?
That's definitely what the big record companies hope.
Market research firm TNS questioned 1,000 people about unlimited music deals.
More than a third said the new services would stop them using illegal file-sharing sites.
But half said they would also stop buying CDs and digital downloads.
What about the Top 40? Could this mean the end of Fearne and Reggie?
It's a fair question. If you get unlimited tracks for free then how do you work out what the most popular songs are?
The Official Chart Company, which calculates all this stuff, has thought about it, and just this week released its first chart based on subscription plays.
At the moment it looks similar to the normal chart but with album tracks making up more of the top ten.
If services like 'Comes With Music' take off, they say future charts could be based on plays as well as sales.