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The second installment of Justin Bieber's "Music Mondays" has arrived.  The star's latest song is called "All That Matters." 

Justin posted audio of "All That Matters" to his YouTube page at midnight Sunday, and followed it up with a link to iTunes for purchase.  When he released "Heartbreaker" in the same way last week, the song shot straight to number one within hours. 

Justin is rumored to have eight more tracks up his sleeve, which he plans to give to fans one by one as his "Music Mondays" social media campaign continues. 

Meantime, the star has released the first trailer for his upcoming "Believe" documentary, which hits theaters this Christmas.  In the clip, he's seen goofing off with friends, as people like mother Pattie Mallette and mentor Usher speak about how mature he's become.  The trailer ends with the words "There's more to his story."

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