And many complained they'd only had a few seconds to prove themselves before being rejected.
Hostess Davina McCall told one group of rejects: "It might be because of your look but unfortunately it is the business we are in."
The first person to get chosen to go through to the next round was 18-year-old Emma from Northampton. She sang Whole Again by Atomic Kitten.
She said: "I really don't know why I've been chosen. I went in there and thought 'let's just go for it'."
The next contestant to go through was Anton, 19, from London. He sang I Believe I Can I Fly by R Kelly for the judges.
He was told by the judges that he had a really controlled voice and sang a difficult song well.
"Geri liked it the most. She was smiling and asking the most questions," he said.