Justin Bieber’s new Christmas album, “Under the Mistletoe” is more “seductive” than past recordings because “vocally, his balls have dropped,” explained his no-nonsense manager, Scooter Braun, to Billboard magazine this week. Proving he’s growing up fast, the 17-year-old’s first release from the album, “Mistletoe,” is sung a few octaves lower than his hit “Baby,” released in January 2010.

PHOTOS: JUSTIN BIEBER

His holiday album, out Nov. 1, includes collaborations with Chris
Brown, Usher, Boyz II Men and Busta Rhymes. But his cover with Mariah Carey of her hit “All I Want for Christmas Is You” was most challenging. Carey agreed to do the duet, as long as Bieber sang in her original high key. “That was the hardest song to do,” Braun told Billboard, adding, “A year ago that would have been no problem.” Bieber also admitted, “Yes, that was high. But I grinded it out, and we got it down.” Bieber will close the holiday season by performing in Times Square on “Dick Clark’s New Year’s Rockin’ Eve With Ryan Seacrest.”