American contemporary a cappella guru Deke Sharon is so impressed with the a cappella scene in Singapore that he likens the standard of the groups here to that in the United States, a hotbed for the genre.

"You would have a hard time finding a city that has as many worldclass a cappella groups as you do in Singapore," he tells The Straits Times in a telephone interview from San Francisco, where he is based. He has been here three times for music events.

Sharon, the vocal producer for the hit musical film franchise Pitch Perfect, singles out home-grown act MICappella for praise. As a producer for the a cappella reality TV competition, The Sing-Off, the 48-year-old had encouraged the group to try out for the Chinese spin-off in 2012 after working with them a few years ago.

The sextet emerged as runners- up and recently released a new album with original works after being signed to major label Universal Music Group.

Sharon will be in Singapore this weekend for the eighth edition of AKA A Cappella, an a cappella festival that is celebrating its 20th anniversary this year. The festival, which last took place in 2012, is organised by local a cappella specialists D-ACA.org and most of the activities will take place at the Singapore Conference Hall.

The line-up includes a concert featuring MICappella and popular Filipino troupe Acapellago, and a series of workshops conducted by Sharon and Australian vocal coach and performance craft expert Zerafina Zara on Sunday.

The Asia-Pacific A Cappella Championship League will also be introduced. Six groups from around the world, including Singapore, Australia and Hong Kong, will battle it out in a knockout-style competition.

Sharon, who is one of the judges, says the competition is akin to the last part in the movie, Pitch Perfect 2 (2015), when the all-female college group, Barden Bellas, compete at the world finals.

He adds with a chuckle: "As you can tell, I'm very excited about this championship in Singapore."

Over the past 25 years, he has worked hard to advocate for a more up-to-date form of a cappella where voices are used to replicate the music of today, be it through beatboxing or vocal percussion.

Apart from working on Pitch Perfect 3 - due out next year and which he prefers to keep mum about - he has a new project Vocalosity, a live a cappella concert which will be touring the US.

Then there is In Transit, a new Broadway musical about the lives of 11 New Yorkers that is set to hit the stage in New York in December. Sharon is in charge of the vocal arrangements, which feature an a cappella score.

All of these projects show that the a cappella scene is still growing, he says.

Referring to Grammy winners Pentatonix, one of the biggest mainstream a cappella acts globally, he notes: "They have more YouTube subscribers than Beyonce."

The American quintet has 11 million subscribers while pop queen Beyonce follows closely behind with 10.7 million.

Sharon adds: "With the Internet and more shows featuring a cappella groups, more and more people are getting interested in the genre all over the world."

And it is about time. Sharon rattles off the long history of a cappella, pointing out that it dates back to more than a century ago.

"Back then, our ancestors were singing a cappella before the onset of instruments. Singing is just fundamental to who we are and I'm just trying to get us back to doing it."