Moses, from London, gave a stirring rendition of Adele's 'Rolling in the Deep', attracting the attention of Sir Tom Jones, Jessie J, will.i.am and Danny O'Donoghue.
Speaking backstage, the 21-year-old revealed that she has in the past been a backing singer for the likes of Gabriella Cilmi and Rihanna.
Summing up the thoughts of the panel, O'Donoghue commented: "I think you did a fantastic job - you really made that song your own. I think your control is incredible, your breathing is incredible."
While deliberating, Moses said: "I'm so humbled by you guys for turning around for me. I honestly don't have a clue who to choose."
In the end, Moses opted for will.i.am, who had promised her: "I know I don't sing like Jessie or yourself or Adele, but I know how to work with good singers and produce them. I know how to take an artist from here to there."
Moses reached the Boot Camp stage of Simon Cowell's X Factor in 2008.
Her Voice song choice had previously been revealed in January by Digital Spy forum members.
Watch Joelle Moses sing Adele's 'Rolling in the Deep' below: