The 32-year-old singer and his band were playing a show with the former Beatles icon in four years ago, and it resulted in one of his most cringe worthy career moments.
He said: ''We performed at Shea Stadium in New York in 2009, supporting Sir Paul McCartney.
''I was introducing each band member as they played a solo, and when it came to my turn, I was supposed to play a piano riff on the keyboard but I hit the wrong button and it came out as drums.
''It sounded rubbish. In front of 50,000 people and a Beatle! That was bad.''
The star - who also appears as a coach on TV singing show 'The Voice' - has been encouraged by the number of hopefuls appearing on the competition with instruments, as he claimed the art of being in a band is being lost.
Speaking to the Mail on Sunday newspaper's You magazine: ''We've seen more people turn up with guitars or playing the piano, and I love that.
''Bands don't get to showcase themselves on TV very often these days.
''It's not very fashionable - bookers are more likely to spend a fortune on Beyonce or Justin Timberlake.''