What was it that drove 600 generally sane men, women and children to don red dresses to swoop, leap and sway to the biggest Kate Bush hit of all time at Melbourne's Edinburgh Gardens last Saturday?
The Most Wuthering Heights Day Ever was a fundraiser to help organisations dealing with domestic violence, as were satellite Most Wuthering Heights Days in Canberra, Adelaide, Brisbane, Sydney, Newcastle and Wollongong.
But the devotees weren't doing it primarily to fight domestic violence, and they weren't doing it only because they liked Kate Bush. They were doing it because of the song: because of what four minutes 26 seconds of Wuthering Heights means to them.
In his just-published book, The Memory of Music, the ABC's Andrew Ford says that while a Beethoven symphony invites us to enter its world, a pop song like Wuthering Heights enters ours; it colonises us, imprints itself on us.
"It is small wonder, then, that we associate pop songs with the time and place in which we most vividly encountered them, the girlfriend we had at the time, the summer holiday we were on, the college we were at," he says.
In most pop songs the repetition begins almost instantly, within seconds, and the fade, beginning mere minutes later, prolongs the sense of endless repetition, sometimes to infinity. Ford says the repetition encourages us "to believe the song will never end, that we still have that girlfriend, that we're still on that holiday''.
Songs are like elevators between floors of our lives. They transport us to where we were when we first heard them: the faces, the places, even the smells.
They are precious, but not necessarily because they are good. When I play songs I find important to my daughter she sometimes dismisses them. Other times she is entranced. I want to believe that those songs take hold of me because they are good. Yet I've got to confront the uncomfortable reality that I first heard most of them between the ages of 12 and 22. It'll probably be the same for my daughter. It's unlikely that the best music of all time happened to happen when I was in my teens and early 20s. It's more likely that those songs are special to me because of exposure; because they were forced on me.
In Hit Makers, released in January, and in Climbing the Charts, released in 2015, authors Derek Thompson and Gabriel Rossman lay bare the brutal way in which it happens.
Hit songs don't "go viral", spreading by infecting one listener after another as is commonly believed, even these days in the age of the internet. They are spread by broadcasting, as are tweets (in this case by uber-tweeters such as Oprah Winfrey).
"It's not so much a million one-to-one shares, as a handful to one to one-million shares," Thompson says.
Rossman has graphed the airplay of hits such as Rihanna's Umbrella. Instead of growing via infection like a virus, it began high and stayed high.
"To explain how so many radio stations came to play Umbrella, we can't resort to arguments about contagion or cascades," he says. "Rather, we must look to something apart from peer influence to explain why so many stations started playing the song so quickly without waiting to see if their peers would play it first."
By the 1980s CBS had been paying $10 million a year to get songs played. As an experiment in 1979 it decided to pay nothing in Los Angeles for Another Brick in the Wall. After all, it was already a hit elsewhere and the band was on tour. The top four stations refused to play it, sales went nowhere, and Pink Floyd's management relented and ordered CBS to hand over the money.
We share our love of special songs with others who grew up loving them, but not necessarily because they are objectively special. Mostly it's because they've been made special.
In The Age and Sydney Morning Herald