Vashon Island Chorale is warming up for an ambitious concert of American music to celebrate its 20th anniversary on the Island.

The concert, featuring works by Leonard Bernstein, Aaron Copland and George Gershwin, will take place at 7:30 p.m. Saturday, April 25, and 3 p.m. Sunday, April 26, at Bethel Evangelical Church.

The program will include a selection of Gershwin favorites including “Sing of Spring,” “Embraceable You,” and “Summertime,” as well as several short pieces by Copland from his series of “Old American Songs.”

“When these songs were composed, Aaron Copland was the pre-eminent American composer, fresh off the successes of his great ballet scores, ‘Appalachian Spring’ and ‘Billy the Kid,’” chorale artistic director Gary Cannon said.

“To aid him in fashioning a uniquely American sound — the definition of which is still argued by musicologists today — he extensively researched musical Americana: slave spirituals, minstrel songs, gospel tunes, hymns, folk songs and the like,” Cannon continued. “In 1950 and 1951, he arranged 10 such songs for solo voice and piano, which we will perform in their very popular choral versions.”

The centerpiece of the concert is “Chichester Psalms,” a cornerstone of American choral writing composed by Leonard Bernstein in 1965.

“Bernstein composed the work as a commission for Chichester Cathedral in England, though it does not include liturgical texts, but rather a selection of psalms to be sung in Hebrew,” Cannon said. “He wrote in a jazzy idiom more closely related to ‘West Side Story’ than to traditional Anglican styles.”

“Chichester Psalms” will feature 13-year-old soloist Alex Patton, a member of the Northwest Boychoir.

It will also boast a quartet that includes soprano Jennifer Krikawa, alto Susan Valenti, tenor Gary Koch and bass Andy Krikawa.

Percussionist Todd Zimberg, organist Paul Swenson and harpist Ashley Wong will accompany the chorale on the Bernstein work.

“I can’t think of a better way to celebrate our anniversary than to share this wonderful music with our Vashon friends and families,” said Jo Ann Bardeen, the chorale’s president.

Tickets to the concert are $10 for seniors and students and $12.50 general admission and can be purchased in advance at Books by the Way and the Vashon Bookshop.

If the concert does not sell out in advance, tickets will also be available at the door.

For more information about the 80-voice Vashon Island Chorale, visit www.vashonislandchorale.org.