This is interesting to me. Although I don’t know enough musicology to understand all the terminology, I found this site concerning the famous opening bars of Wagner’s opera Tristan und Isolde, one of the most influential chords in music but open to analysis.
Until recently, I hadn’t realized that the chord which begins the Beatles’ song, “A Hard Day’s Night,” had also been subject to debate and analysis!
I’ve known that song since I was seven years old! You learn something every day. Like the Tristan chord, the "Hard Day's Night" chord is difficult to identify.
Both, however, have become greater than their original context. This quote from the first website applies to that Beatles’ chord, one of the most famous in rock and roll, “[I]n the words of Robert Erickson (1975, p.18), ‘among other things, [the chord is] an identifiable sound, an entity beyond its functional qualities in a tonal organization.’"