Universal Music Group will be well represented at a press event Google has scheduled for Wednesday, but conspicuously missing will be two of the other top-four record companies.

Google

Google sent invitations today for a press event, to be held in Los Angeles, where the company is expected to add downloads to its cloud music service, as well as unveil social-networking features.

CNET has learned that Google has signed a licensing agreement for the new service with Universal Music Group but does not have deals in place with Sony Music Entertainment or Warner Music Group, according to multiple industry sources. It is unclear whether EMI would participate. Talks between Sony, Warner and Google continue, the sources said.

The negotiations between Google and the labels by and large haven't gone well for either side. The labels are eager for a serious iTunes competitor to emerge and believe Google has the technological know-how, money, and Internet presence to give iTunes a run for its money.

On the other hand, Google wants to offer first-class music and movie services to users of Android, the company's powerhouse mobile operating system.

Google has a tense relationship with some of the record companies. In general, the search company's past dealings with media companies has at times been acrimonious. Most notably was Viacom's accusations in a $1 billion copyright suit it filed against Google that the company encouraged YouTube users to post pirated clips to the site.

For the past two years, Google has attempted to improve relations with content creators. Managers boosted antipiracy efforts and helped Vevo, the Internet music-video service, get off the ground.

Despite that, Google is once again launching a major part of its music service without acquiring licenses and this may serve to widen the rift between the company and some of the labels.

Google launched the test version of its cloud music service earlier this year without licenses.

The labels argue that for Google to challenge Apple and offer a feature-rich service, the search company needs music from all the top record companies as well as all the licenses. Google apparently sees it differently and next Wednesday we will learn more about how Google plans to compete without songs from some of the the top labels.

What could also aggravate record-company execs is a disagreement over a request by the labels' trade group to remove a popular but controversial music app from the Android Market.

The Recording Music Industry Association of America has alleged, according to PCMag.com, that MP3 Download Pro enables users to download music to their mobile phones and is being used for piracy.