Two of the defendants argued their innocence on Sunday in a webcast
Half of the charges levelled at the founders of the Pirate Bay file-sharing site have been dropped.
Swedish prosecutors dropped charges relating to "assisting copyright infringement" leaving the lesser charges of "assisting making available copyright material" on trial day two.
Pirate Bay co-founder Frederik Neij said it showed prosecutors had misunderstood the technology.
The music industry played down the changes as "simplifying the charges".
Peter Danowsky, legal counsel for the music companies in the case, said: "It's a largely technical issue that changes nothing in terms of our compensation claims and has no bearing whatsoever on the main case against The Pirate Bay.
"In fact it simplifies the prosecutor's case by allowing him to focus on the main issue, which is the making available of copyrighted works."
The Pirate Bay was launched in 2003 and quickly established itself as the world's most high profile file-sharing website. In February 2009, it reported 22 million simultaneous users.
At the start of the trial in Stockholm, Frederik Neij, Gottfrid Svartholm Warg, Peter Sunde Kolmsioppi and Carl Lundstrom were facing a large fine and up to two years in prison, if convicted.
"This is a sensation. It is very rare to win half the target in just one and a half days and it is clear that the prosecutor took strong note of what we said yesterday," defence lawyer Per E Samuelson told the TorrentFreak website, which reports on developments in the BitTorrent file-sharing community.
BitTorrent is a legal application used by many file-sharers to swap content because of the fast and efficient way it distributes files.
No copyright content is hosted on The Pirate Bay's web servers; instead the site hosts "torrent" links to TV, film and music files held on its users computers.
At the turn of the century lobbyists proclaimed that travelling in a steam-driven train at the mindboggling speed of 20 mph would suffocate and kill you. This nonsense came from rigid old fashioned entrepreneurs who couldn't cope with the tide of time, and the change in technology that comes with it. Nor can the media barons of large companies and if they can't they will subsequently disappear and others will take over. The trial is at best entertainment but of no significance what so ever! Fredrik, Malmo, Sweden
I sincerely hope that the media firms fail miserably in this endeavour. They need to recognize that websites like the Pirate Bay and people like Mr. Sunde and his colleagues will be around for quite a while mostly in response to their dreadful business tactics. These firms don't even have a valid accusation: "It's a trial that regards four individuals that have conducted a big commercial business making money out of others' file-sharing works, copyright-protected movies...". What business? None of these bit-torrent trackers are a business! Most of their money goes right back into the site itself! Any money they make has got to be a fraction of the ridiculous amount these lawyers are asking for! And none of the "infringing material" is found on their servers anyway! It'll set a welcome legal precedent when the firms lose and TPB gets to continue freely, and the media bullies can leave with their tails between their legs. Good luck TPB crew! Zenman, New York, NY
If you can get something for nothing, why buy it? This is theft, pure and simple, and it deprives the creators of the profits they have earned and that they need to produce more content. Daniel Guida, La Mesa, California, USA
I'm with Pirate Bay on this one as the entertainment industry has been ripping off consumers for decades and now with the digital age it's time to stuff a few of these companies… If they ain't prepared to keep apace with technology and offer their product at a reasonable price then they're finished. And as far as the law goes, these two lads are in the right - they are not responsible themselves for distributing the il(legal) content. So, stuff the industry. Les, Elgin
Regardless of whether or not I can download content from sources on the net, legally or illegally, I still buy CDs, DVDs, video games & books. I think most, not all, people, like myself, use the internet to get a better idea of a product before they purchase it. I'd rather know that an album has only the one song on it that I like that I've already heard on the radio many, many times before I go and buy a copy, only to be disappointed. That's just me, though, but I know I can't be that unique or original in my thinking. Amy, Portland, Oregon, USA