Apple iTunes and Amazon MP3 store, take notice. Google may be joining your ranks as a retailer of online music.

The online search giant has a press conference scheduled for tomorrow—and many believe it is to announce the launch of a previously rumored online music store.

Several sources, including the Los Angeles Times, have reported that Google has been actively courting the major music labels over the past year in attempts to secure online rights to various libraries of songs. Various news sites claim Google has yet to secure those rights from Sony's music arm or Warner Music Group.

But undisclosed sources have told Bloomberg Businessweek that Google may have already signed up EMI Group and is "near an agreement" with Vivendi SA's Universal Music Group. That, say the sources, would allow Google to offer online tunes from various, highly popular recording artists such Justin Bieber, Coldplay, Lady Gaga, and Katy Perry,

According to sources close to Google's online music plans, tomorrow's announcement will outline an expansion of Google's locker service which will allow users to store music online and play their tunes from "the cloud" on multiple devices. Details on how music can be legally shared among friends on Google+, the company's social network site, are also planned, say the undisclosed sources.

Google Said to Be Near Universal Music Deal for Song Downloads [Bloomberg Businessweek]
Google courts record companies before its planned music store debut [Los Angeles Times]
Google to Open Digital Music Store on Wednesday [Rolling Stone]