SURPRISE PERFORMANCE: Jennifer Moss starts a 'flash mob' with ukuleles and a choir singing Let It Be in The Plaza.

Disguising their ukuleles in shopping bags, a 25-strong group of musicians joined by 50 singers shocked hundreds of people in The Plaza foodcourt on Saturday with a seemingly spontaneous performance.

The "flash mob's" performance of The Beatles' Let It Be in the Palmerston North shopping mall had outsiders joining in the sing-song, and hundreds of curious bystanders rose to their feet to see what was going on.

The performance was the brain-child of musician Jennifer Moss, who runs the Manawatu Ukelele Group and the Manawatu Community Choir, both of which were involved.

It was four months in the making and required co-operation from The Plaza, which turned its music off moments before and made sure security was informed on the day.

The opening lines were sung by Ms Moss and the result, she said, was fantastic.

"When the others started to sing this rush came over me," she said.

Responses ranged from shocked and surprised to delighted, she said, and the perplexed look on some people's faces was brilliant.

"Once I got over starting, I just actually pretended I was in my living room," she said.

The song was chosen because it was well known. It was evident that more than just the choir took part, she said.

The inspiration behind the performance was just to provide entertainment and bring music into the lives of Palmerston North people.

Spectator Kelly Davis was having lunch with a group of friends when the performance erupted.

"It was cool, the ukuleles were cool," she said.

"We just saw people standing there watching."

She would be keen to see more "random stuff" like the flash mob happen in Palmerston North.