Radiohead's 10-track studio album In Rainbows became available Wednesday for download from their official website, with fans invited to pay what they want.

The British alternative rock band are not revealing how many people have ordered the album or what they agreed to pay.

Thom Yorke, lead singer of the British band Radiohead performs in Paris in August 2006.  Thom Yorke, lead singer of the British band Radiohead performs in Paris in August 2006.
(Stephane de Sakutin/Getty Images)

Getting an independent assessment of how much is sold — and whether the experiment is a success — will be difficult, as the sales will not turn up on regular sales-ratings charts

However, Billboard and other music trade sources say tens of thousands of downloads have gone ahead — and after some initial heavy traffic, the process appears glitch-free.

Some downloaders are complaining about the bit rate for In Rainbows.

Bit rate determines the audio quality and how much space an MP3 file takes up on a computer or MP3 player.

In Rainbows is encoded at 160 kbps — higher than the default iTunes rate of 128 kbps, but lower than 320 kbps, seen by some music fans as the only encoding rate worth paying for.

Postings on Radiohead message boards complained that the band did not notify fans of the audio quality.

The experiment is being regarded as a test of a new approach to selling music: instead of fighting downloads, the band is embracing it, with the record labels cut out of the equation.

Meanwhile, Nine Inch Nails announced they were following the band's lead and dumping their record label.

"As of right now Nine Inch Nails is a totally free agent, free of any recording contract with any label," lead singer Trent Reznor wrote on the band's website.

"I have been under recording contracts for 18 years and have watched the business radically mutate from one thing to something inherently very different and it gives me great pleasure to be able to finally have a direct relationship with the audience as I see fit and appropriate."

Many indie bands already offer their music free online, with the hope of building the number of fans who will buy concert tickets instead of records.

Radiohead have scored number one positions for their last three studio albums — Kid A, Amnesiac and Hail To The Thief.

It has also agreed to issue a CD of In Rainbows next year.

With files from the Associated Press