Emma Willis presents the live semi-final, as the eight remaining singers perform for a place in next week's final. The contestants mentored by their team leaders - Olly Murs, Jennifer Hudson, will.i.am and Tom Jones - sing their hearts out, all hoping to get one step closer to winning a recording contract. Four acts will be going home tonight, and for the first time this series all the power lies with the viewers at home. Who will the public vote to save tonight?