Rock band Van Halen’s reunion tour fell into disarray on Monday when it announced it would postpone all shows through April 19 while guitarist Eddie Van Halen undergoes tests for an unspecified medical condition.

The news came a week after the group postponed four shows for the same reason.

Seventeen shows are now affected, beginning Tuesday in Charlottesville, Va., and running through April 15 in Baltimore, which was one of the four postponed last week. The next scheduled show is set for April 19 in Las Vegas.

According to organizers, Van Halen, 53, who has battled cancer and substance abuse, “is currently under doctors’ care” and will “continue medical tests to define a course of treatment.” No further details were made available.

Fans are being asked to keep their tickets, which will be honored at makeup dates to be announced.

Van Halen returned to the road last fall with original lead singer David Lee Roth for the first time in 20-plus years. The tour, which features Eddie Van Halen’s teenage son Wolfgang on bass in place of co-founder Michael Anthony, has routinely sold out North American arenas.

Nine Inch Nails is utilizing the Internet to disseminate its new instrumental album, ‘‘Ghosts I-IV,’’ which went live at 8 p.m. Sunday via the Trent Reznor-led group’s Web site. ‘‘Ghosts’’ also will see physical release via RED Distribution on April 8.

Fans can receive the first nine songs from the 36-track project, which was recorded during ‘‘an intense 10-week period last fall,’’ for free, or the entire album can be obtained digitally for $5.

‘‘I’ve been considering and wanting to make this kind of record for years, but by its very nature it wouldn’t have made sense until this point,’’ says Reznor, who collaborated on the music with Alan Moulder, Atticus Ross, Alessandro Cortini, Adrian Belew and Brian Viglione. ‘‘This collection of music is the result of working from a very visual perspective — dressing imagined locations and scenarios with sound and texture; a soundtrack for daydreams. I’m very pleased with the result and the ability to present it directly to you without interference.’’

There are several other ordering options available for ‘‘Ghosts I-IV,’’ each of which come with immediate access to the album in digital form. The standard double-CD set is retailing on Reznor’s site for $10, while a $70 deluxe edition in a hardcover fabric slipcase includes the audio CDs, a DVD with multi-track files for the music and a Blu-Ray disc with high-definition stereo mixes.

For $300, devotees can opt for the ‘‘ultra-deluxe limited edition’’ package, which features all the elements in the deluxe edition plus a four-LP vinyl set and two Giclee prints amid ‘‘luxurious packaging.’’ This edition is limited to 2,500 copies and is autographed by Reznor.

Both deluxe editions will ship on May 1; a stand-alone four-LP set will be available April 8 at traditional retail. Interested parties can sample a host of the tracks from NIN’s site. The full download is also available from Amazon.com, to which it was delivered by TuneCore, while the first 9 tracks were uploaded to BitTorrent sites like the Pirate Bay.

Demand for the new music appeared to be immediate and heavy. Just after 8:30 p.m., the site was down temporarily due to traffic.

Nine Inch Nails’ contract with longtime label Interscope expired last October. Interscope then released a remix album, ‘‘Y34RZ3R0R3MIX3D,’’ and holds the rights to release a greatest hits collection at some point in the future.

As a precursor to the online release of ‘‘Ghosts,’’ Reznor collaborated with Saul Williams on an album dubbed ‘‘The Inevitable Rise and Liberation of Niggy Tardust,’’ which was offered as a free download in 192kbps MP3 form, or as a higher fidelity 320kbps MP3 or FLAC version for $5. Initial statistics revealed only 18 percent of fans chose to pay for the album.

Reznor’s move also follows Radiohead’s ‘‘name your own price’’ download scheme for its ‘‘In Rainbows’’ album last fall. And while both acts have jumped ship from major labels to release music completely independently, one source close to NIN believes the differentiation between the approaches of artists in this position will actually be what changes the game.

‘‘Most of the time with a label, they try to squeeze that differentiation out,’’ the source told Billboard last fall. ‘‘Now, there’s nothing that stops Reznor or Radiohead from doing it uniquely their way. They can do it how it best works for them, without pressure.’’

Three global record companies have launched legal proceedings against China’s top Internet search engine, Baidu.com Inc, accusing it of violating copyright by giving access to music files, an international music trade body said.

Universal Music Ltd, Sony BMG Music Entertainment (Hong Kong) Ltd and Warner Music Hong Kong Ltd have asked a court to order Baidu (BIDU.O: Quote,Profile, Research) to remove all links on its music delivery service to copyright-infringing tracks they own the rights to, the International Federation of the Phonographic Industry said in a statement.

The claims have been filed with a court in Beijing, said IFPI, which is backed by global music industry heavyweights.

Separate action is also being taken by Universal Music Ltd, Sony BMG Music Entertainment (Hong Kong) Ltd, Warner Music Hong Kong Ltd, as well as Gold Label Entertainment Ltd against Chinese media firm Sohu.com Inc (SOHU.O: Quote, Profile,Research) and its search engine, Sogou, the statement added.

In January 2007 Baidu and EMI Music, the fourth major global record company, launched an advertising-supported online music service in China.

Baidu’s shares fell 6.9 percent to close at $253.49 and Sohu’s shares fell 5.43 percent to $46.29 on the Nasdaq on Tuesday.

Yahoo China also faces proceedings after refusing to comply with a ruling in December by the Beijing Higher People’s Court, which confirmed the company violated Chinese law by committing mass copyright infringement, IFPI added.

Led Zeppelin might not be headed over the hills and far away quite yet — the recently reunited rock legends have let it slip that they may actually perform together again after all, but not before September.

Guitarist Jimmy Page revealed the scenario over the weekend, according to Reuters, saying that the legendary band’s one-off, strongly received December reunion gig in London, which sparked rumors of a world tour, was likely a precursor to more shows.

“I can assure you the amount of work that we put into the O2 [concert], for ourselves rehearsing and the staging of it, was probably what you put into a world tour,” Page said, adding that more shows are off for the moment because of singer Robert Plant’s commitments to touring with bluegrass star Alison Krauss in support of their Grammy-nominated joint album, Raising Sand.

“Robert Plant also [has] a parallel project running, and he’s really busy with that project, certainly until September, so I can’t give you any news,” Page added.

In an interview with New York’s Madison Square Garden Network during halftime at a Knicks game on Friday, Plant also opened the door to more shows, saying, “You never know what is around the corner. It’s just nice to play with those guys,” when asked about Zeppelin tour rumors.

That’s a sharp contrast from what Plant said in late September, when he shot down claims of a potential tour outright. “There’ll be one show and that’ll be it,” he told British music mag Uncut.

Plant’s remarks had come days after Foo Fighters frontman Dave Grohl apparently volunteered his services for a potential Zep tour. After saying that he had planned to sneak his way into the long-sold-out London show, the former Nirvana drummer added that he wouldn’t mind manning the kit for Led Zeppelin if needed. “[I am] at their beck and call,” he told British music weekly the New Musical Express.

Last.fm (www.last.fm) today announced that it is launching a service to allow anyone to listen to music on the site for free.

Last.fm has become one of the leading places in the world where people can go to listen to music online. Its vast library has attracted a community of more than 20 million unique monthly users in 240 countries around the globe. The heart of Last.fm is a powerful recommendation engine that guides listeners to music they are likely to enjoy based on prior selections, connecting them with the music they love and with others who share their tastes.

In launching this service, Last.fm becomes the first music website to offer free, global, on-demand access to the largest licensed catalogue of music built on partnerships with all four major record labels - including Universal Music Group, Sony/BMG, Warner and EMI - as well as CD Baby, IODA, the Orchard, Naxos and more than 150,000 independent labels and artists.

Last.fm’s free-on-demand service will be advertiser supported, allowing clients many unique opportunities to reach a highly targeted and engaged audience.

Last.fm was acquired by the CBS Corporation on May 30, 2007.

“It is clear to us that communities built around great content are increasingly driving traffic and revenue online,” said Leslie Moonves, President and CEO of the CBS Corporation. “We acquired Last.fm because music is one of the best ways to build communities on the internet. Adding such a tremendous collection of content to Last.fm will help it grow by leaps and bounds. The skill set that we’re learning along the way will be very important as we build additional online communities around our other world-class content as well.”

Martin Stiksel, Last.fm co-founder, said: “We’re giving the listener free access to what is basically the best jukebox in the world. The ability to dip into such a uniquely broad catalogue from your laptop, home or office computer, and listen to whatever you want for free represents a new way of consuming music that in turn might change the way you listen to music. In that respect, nobody else can currently offer what Last.fm is offering right now.”