The pair went head to head on a cover of James Morrison track Broken Strings as the coaches whittled down their acts to just five.
"I think the pairing of these two is great, they've got both very modern voices," the pair's coach Danny said.
Aleks however felt intimidated by his more experienced opponent. "She's good... I've never performed a duet with a girl... or a boy... or anyone," he confessed.
Danny however gave the cheeky teen a pep talk: "I've heard you sing, and I see a little bit of myself in you, you have to believe in yourself."
After the performance there was no clear winner for Danny.
He said: "To try and put something in between the two of you... Emmy, I think you’re further on down the line than Aleks is.
"But Aleks, I think I have a lot to show Aleks in a way. So... I’m going to base my decision on my role on this show, which is a coach, and I think the person who is going to go through to the live shows with me, is Aleks."
View a clip of Aleks Josh below...