Christina Aguilera Pictured Recording 'Something Special'

Wearing a white casual shirt, the coach of 'The Voice' is seen singing in front of a microphone.

Christina Aguilera is apparently working on her new music. The 33-year-old pop superstar took to Twitter on Tuesday, December 24 to post a picture of her singing into a microphone in front of her Christmas tree.

"Working on something special... Happy Holidays to all!! XoXtina," the singer captioned the snap. However, there's still no word on what kind of "special" project she's working on or when it will be released.

Aguilera had a busy 2013. Earlier this year, she worked with New York duo A Great Big World for a song called "Say Something". The track peaked at No. 4 on Billboard 100.

The former Disney star also spent the past few months working in the fifth season of NBC's singing competition "The Voice", where she appeared as a coach alongside Adam Levine, Blake Shelton and Cee-Lo Green.