"Welcome! South entrance, move to the left, please!" screams Ms Limin Ng, 21, one of the hundreds of volunteers here at the Padang. She has been on duty since 10am, and will remain until everyone leaves, at around 11pm.
Who volunteers to do this? To stand in the sun all day, shouting yourself hoarse, giving directions, helping the disabled and elderly get to their seats?
Ms Ng, a biological sciences student at Nanyang Technological University, says she is enjoying it, although her sister told her she was crazy to want to do it.
"When you help someone and you smile and they smile back, you feel like you've accomplished something," she says.
It is as simple as that. Yet, it is not often that you meet people like Ms Ng, who ask for nothing more than a chance to help.
Near her, just before the start of the National Day Parade, is one spectator who has a special stake in today's Golden Jubilee celebrations.
Mr Ong Eng Hin, 63, marched in the first Parade, in 1966, as a student with Raffles Institution's semaphore flag group; in the next three Parades, he marched as a scout. Now, after a long break, he has come back, as a spectator.
"No lobang for a ticket lah," says the accountant, when asked why it took so long for him to return. As luck would have it, this year, a friend gave him two tickets, so he is back - five decades after marching in the new republic's first Parade.
Others at today's festivities were not around to witness Singapore's forced independence in 1965. In fact, some were citizens of other countries until fairly recently.
Twenty years ago, Ms Jasmine Lin, 45, had just arrived from China, and thought it might be interesting to watch the Parade at the National Stadium. Having been given a ticket by her boss, the marketing executive at a food and beverage company is back this year - this time as a citizen of Singapore.
Now a mother of a 17-year -old daughter ("made in Singapore", she quips), she became a Singaporean in 2003, and came here today to mark her 20 years of residency.
"I just want to celebrate with other Singaporeans," she says.
Travelling to more than 30 countries for work has opened her eyes to how much her adopted home has to offer. "It makes me think more about what I have in Singapore," she says.
Among the spectators is a Singaporean family who live in New York City but return regularly during the summer school holidays.
On this vacation back home, the children are here to see their grandparents and "go swimming", says daughter Kai-Lin, 11 - just as management consultant father Kwek Ju-Hon, 40, prompts her to add "and SG50!"
In spite of the cue, they seem genuinely excited to be here, along with mother Stephanie Rupp, a professor of anthropology. Son Kai-Shan, nine, is looking forward to the mobile military display.
Snare drummer Leonard Chen, who marches with the Singapore Armed Forces Central Band, was in one of the early displays. He is just one dot on a field composed of hundreds of dots - but that is fine with him. The baby-faced 25-year-old, whose main instrument is actually the piano, has performed in three Parades, so he considers himself a veteran.
Today's programme - featuring complicated marching and musical synchronisation with the Silent Precision Drill Squad and the Association for Persons with Special Needs - will not be a problem for the band. He and his team have been training since April to make sure the six-minute sequence is perfect.
No, he will not be that guy on the field who marches left when the whole company marches right, he says. Not today.
"This is the biggest show in Singapore history, and I'm proud to be part of it," he says.
Overseas citizens returning here for a once-in-lifetime event, foreigners who became Singaporeans by choice and a middle-aged man who was there as a boy at Parade No.1 - I suppose, for volunteer Limin Ng, now hours into her shift, they are three reasons she does what she does.