Everyone is in for some surprises when the Call and Response artists unveil their seventh exhibit this Friday at Oregon State University's Giustina Gallery.

And that includes the artists.

The artists follow the same formula every year leading up to the exhibit: one artist creates their own "call" piece, using a medium of their choice, and the other artists make a "response" to each of the call pieces. The artists don't get to see the response pieces until the show opens.

The popular show has a new theme each year, which keeps it fresh and exciting for the eight mid-valley artists and viewers, says artist Mariana Mace.

"Every year we're starting from ground zero and even though the idea is seven years old it's like it's different because the parameters change," she said.

For Call and Response VII, the focus is "Natural Structure." The show includes a special artists' reception and gallery talk Sept. 8, and will be on display through Sept. 29.

Each artist created eight pieces (one call work and seven responses), for a total of 64 total works on display. Each group is displayed with one artist's call piece followed by the seven responses, Mace said.

The artists, who have been together about a decade, meet up and exchange call pieces in a box or wrapped in brown paper, so no one knows what they're getting until they leave. Each artist is then given about a month to complete their responses, before moving onto the next call piece.

Mace didn't want to elaborate much about what natural structures may be featured in the exhibit to avoid spoiling it for her fellow artists.

She said the subjects range from things visible only through a microscope to items visible in nature.

Mace is a basket maker who also works with felt. The other participating artists are photographer James Schupp, painter Anita Cook, textile artist Karen Tornow, glass artist Sally Ishikawa, ceramic artist Jeff Gunn, and painter and mixed media artist AliceAnn Eberman.

The eighth and newest member, Rob Dudenhoefer, is hard to categorize, Mace said.

She knew him as a jeweler, but last year for "Call and Response VI: Urban Textures" he brought his artwork to the gallery in a pickup truck with a trailer, dolly and hand truck.

"He had done all of this monumental garden sculpture stuff, as well as a little bit of jewelry. So, you never know what to expect from him," Mace said.

This year, Dudenhoefer has worked with smaller sculptures, she said.

Mace said having to respond to all these different forms of media for responses is a challenge and forces the artists to step outside of their comfort zones.

"How do I respond to that photograph with a basket? I'm glad I can do some other things besides baskets," she said.

The annual exhibit attracts many return visitors who are curious to see how the artists interpreted the theme, Mace said.

"We've heard a lot of comments from people that this is one of the best shows they go to, so it makes us feel really good," she said.