The humble 'ukulele is bigger than ever.

"The fever is spreading around the world," said Roy Sakuma, veteran 'ukulele instructor.

And he should know.

For at least three decades, he has been the heartbeat of the annual 'Ukulele Festival, which will be held Sunday at the Kapi'olani Park Bandstand. Starbucks has become the title sponsor, with support from the Waikiki Beach Marriott hotel, to keep the uke fest afloat.

"There are uke festivals all over the United States and all over the world. People keep telling me that the 'ukulele is getting real popular in New Zealand and Australia, too," Sakuma said.

Local manufacturers such as Kala 'Ukulele are busier than ever, keeping up with the demand for the instrument. "They've brought the uke to the Far East and all over Europe. I'm shocked - Denmark, Switzerland, Holland, France and Germany."

And Tony Coleman, a Canadian filmmaker, has been here to do some footage for "Mighty Uke," a documentary that will showcase the surging popularity of the uke. Coleman has been interviewing Sakuma, Jake Shima-bukuro and Bill Tapia, names connected to the uke, as he explores the phenom on three continents and at least a dozen U.S. cities.

"The 'ukulele has become the instrument of choice for people all over the world, Hawai'i included," Sakuma said.

He and his wife Kathy operate the Roy Sakuma 'Ukulele Studios, and they see young students coming in to strum every year.

"Local children are terrific," Sakuma said. "It's always the case. All kids love the 'ukulele. When I go to schools to play the uke and teach them how to play, it always hits the right notes."

The keiki always get a hearty response from the festival audience.

The uke's portability makes it a popular party instrument, even more easily transportable than a guitar.

It hasn't hurt, too, that Israel Kamakawiwo'ole, Hawai'i's best-selling musical artist (think "Over the Rainbow"), traditionally strummed the uke as his principal instrument.

And Shimabukuro, he with the nimble and incredible fingers and rock-star charisma, has done his share of exposing the dynamics of the little four-stringed instrument.