system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: For someone who doesn't understand music or music theory at all, what exactly is the big deal about "A Hard Day's Night"'s opening "chord"?
gpt
Without going too far into details about the notes, it was essentially a chord people couldn’t figure out for a little while. No instrument or 12 string guitar could recreate that same sounding chord. Later they found out that the frequencies of the chord were so unique because each member played a chord or a note from that chord at the same time, but the piano included an f note that could not be played on the guitar when holding that specific chord. 

tl;dr - the beatles threw in a rogue f note during that chord that made it sound so unique.