The loud circus music was drowned out by cries of disbelief from the crowd as a pair of buskers juggled six sharp knives over a volunteer lying on his back.

Instinctively, the man covered his eyes, held his breath and hoped for the best.

Outside Ion Orchard, the Annoying Brothers mesmerised the 200-strong crowd that had gathered to watch them juggle, spin and pull off acrobatic stunts.

Among the street performers who have become a common sight in Orchard Road, Mr Jonathan Goh, 20, and Mr Edwin Ong, 25, stand out for their ability to make passers-by stop and stare.

Enamoured with the circus since they were children, the duo decided to combine their acts to up their game three years ago.

Mr Goh, an arts business management student at Ngee Ann Polytechnic, had wanted to busk since seeing foreign buskers show off their skills in Singapore when he was 15. Mr Ong started simple juggling acts for the community when he was 14. Their supportive family members often share their busking videos on Facebook.

The friends met at Bornfire Community Circus, an interest group at the Kallang Community Club. When they decided to pair up, they started with simple acrobatics and juggling, and added more acts such as knife-juggling, plate-spinning and comedy tricks as they got better. "I used to practise every day after school until it got dark when I first started," said Mr Goh.

The spontaneous nature of performing in the streets means the duo improvise on the go, having devised a secret code of communication with each other.

"We have to be really quick-witted because people are just walking past and we have to catch their attention in that short five to 10 seconds," said Mr Ong, an engineering student at Nanyang Technological University.

According to the National Arts Council (NAC), there are 200 registered buskers, with more than half below 35 years old.

"Over the last decade, busking in Singapore has gained greater visibility and acceptance, which may be attributed to general public's greater appreciation of the arts," said NAC arts and community director Chua Ai Liang.

Buskers must go through an audition before they receive a letter of endorsement - their ticket to perform for a year. It indicates up to five designated busking sites where each busker may perform on a "first come, first served" basis. There are about 80 sites.

The passion and skill of the Annoying Brothers are evident as they put the lie to their name, making the audience smile and laugh show after show.

They make enough money to cover their daily expenses and invest in new circus props.

"There is this intimacy that I can communicate with the audience when I perform," said Mr Ong. "And the satisfaction from the appreciative audience keeps me going back week after week."