Its a magic chemistry. A song about a hobo who jumped into a pond. Another song that no one is sure of the meaning; Nah nah nah nah nah nah nah nah nah nah nah, hey Jude! This continues for 7 minutes.  Sung for the joy of singing. A moment for the ages.  Thousands together, bonded by a common spirit, loving it.

"Waltzing Matilda" is Australia's most widely known bush ballad, and has been described as the country's "unofficial national anthem".
The original lyrics were written in 1895 by Australian poet Banjo Paterson, and were first published as sheet music in 1903. Extensive folklore surrounds the song and the process of its creation, to the extent that the song has its own museum, the Waltzing Matilda Centre in Winton, Queensland, where Paterson wrote the song.

Some lyrics go like this:

Once a jolly swagman camped by a billabong
Under the shade of a coolibah tree,
And he sang as he watched and waited till his billy boiled:
"Who'll come a-waltzing Matilda, with me?"

Down came a jumbuck to drink at that billabong.
Up jumped the swagman and grabbed him with glee.
And he sang as he shoved that jumbuck in his tucker bag:
"You'll come a-waltzing Matilda, with me."

Up rode the squatter, mounted on his thoroughbred.
Down came the troopers, one, two, and three.
"Whose is that  jumbuck you've got in your tucker bag?
You'll come a-waltzing Matilda, with me."

"Hey Jude" was released in August 1968 as the first single from the Beatles' record label Apple Records. More than seven minutes in length, it was at the time the longest single ever to top the British charts. It also spent nine weeks at number one in the United States, the longest for any Beatles single. "Hey Jude" tied the "all-time" record, at the time, for the longest run at the top of the US charts. The single has sold approximately eight million copies and is frequently included on professional critics' lists of the greatest songs of all time. In 2013, Billboard named it the 10th biggest song of all time.

Hey Jude, don't make it bad
Take a sad song and make it better
Remember to let her into your heart
Then you can start to make it better

Hey Jude, don't be afraid
You were made to go out and get her
The minute you let her under your skin
Then you begin to make it better
Nah nah nah nah nah nah, nah nah nah, hey Jude!

These two songs could not be more different. Written almost 100 years apart. One is a ballad, first a poem, then set to music years later. The other is a hit song composed by the Beatle, Paul McCartney.
They have one thing in common. Both are sung by crowds of 80-100,000 at major sporting events. You hear "Waltzing Matilda" at the closing ceremony of the 2000 Olympics in Sydney, Australia. Then you hear "Hey Jude' in Manchester"s Etihad Stadium, before the football match.
For me this is special, when it happens. Music, singing and a great sport event. All together. I am reminded that humans can do good things.