Speaking to Digital Spy about Cowell's reaction, Blackledge admitted: "First of all, he seems a nice guy to me. He knows what he's talking about. He's been in the industry for a million years.
"He's entitled to his opinion, and there's that saying, 'You can please most of the people most of the time, but nobody can please all of the people all of the time'.
"I've never met Simon before I walked out on stage, but I think he has a history of not liking the organ so I had this fear before I even walked to the organ he would buzz me. But, you know, he gave me a chance."
However, Blackledge conceded that he wishes Cowell had been "slightly gentler", admitting: "It could have been nice if he liked it."
Britain's Got Talent continues on Saturday at 8.45pm.
Watch Graham Blackledge's Britain's Got Talent audition below: