Lopez a cappella group Lopez Sound has invited some very special guests to perform on the island.

International barbershop music champion Friendly Advice is joining Lopez Sound for an evening of “a cappella entertainment at its best” on Saturday, May 31, 3 p.m. at Lopez Center. The Chordsmen, a chorus of 20 from Friday Harbor, will also make an appearance, singing American classics.

Lopez Sound met Friendly Advice at the Barbershop Bonanza concert in Friday Harbor last spring, where the groups both performed. “Incidentally, we are both invited to sing again this year!” said Lopez Sound founder and leader J.C. Marean.

The members of Friendly Advice all live in Washington and are recognized as one of the best barbershop quartets in the world. “I have a very high regard and profound respect for good barbershop music. Friendly Advice is not good barbershop music, it is the best barbershop music. They are world champions. And I know a lot of people on Lopez like that kind of music,” said Marean.

Lopez Sound, which has been enchanting audiences for five years, will perform its usual eclectic mix of songs, including work from Duke Ellington and Cole Porter, among others, and two songs they’ve written. Many of the classic songs they will perform are of Lopez Sound’s own arrangement.

“It’s going to be good music, great humor, and wonderful entertainment. It’s really going to be fun. It’s American music: jazz and barbershop. Music that is uniquely American in origin,” said Marean.

Tickets are $12 and only available at the Lopez Center office and at www.lopezcenter.com.