Coming face-to-face at training and education centre in Jamaica, Gary told the third in line to The Throne: ''I've started the Diamond Jubilee song and we're hoping to get you on a track.''
According to the Daily Mirror, Harry protested: ''I can't sing,'' to which Gary pushed: ''Tambourine? Just one hit?''
The royal is currently visiting Commonwealth countries as part of his Diamond Jubilee tour, closely followed by Gary who is gathering material by unknown artists for the record.
And the father-of-three - whose wife Dawn is pregnant with their fourth child - still believes he has a chance of snaring Harry.
He added: ''I'm sure we'll get him, he'll do it for the cause.
''We've not got experienced artists on this record we've got undiscovered people, we're going from Australia to Kenya and the Solomon Islands.
''It's all being recorded on a laptop, when we get back to London we're going to Abbey Road studios to mix it.''