It was 50 years ago this summer that The Beatles released their first movie, 'A Hard Day's Night', and the iconic soundtrack that came with it.

That means for five decades, musicians and music historians have been trying to figure out exactly what makes up that legendary opening chord to the movie's title track.

There have been a lot of theories, but one rock icon went to the 'mecca' of all things Beatles - the Abbey Road Studios in England - to listen to the original recording of the opening chord to 'A Hard Day's Night', with some help from Giles Martin, son of Beatles' producer George Martin.

At Abbey road, Randy Bachman, founding member of both The Guess Who and Bachman-Turner Overdrive, unlocked the secret to what he calls:

The most famous chord ever on a 12-string guitar.

He shares his findings (in great detail) with the Canadian Broadcasting Company:

One note about the song 'A Hard Day's Night':

The time the title of the movie was selected to the time the song was written and recorded by The Beatles was less than 24 hours.

They were THAT good!