The Colorado State University a cappella group Mainstreet demonstrated their passion for music Wednesday night at their spring showcase.

With the theme of “Through the Decades,” Mainstreet performed their first themed showcase event. They walked the audience through some of the classic hits of each decade starting with the 60s and “Build me up Buttercup” and ending with an Adele mashup arranged by Mainstreet’s Drew Moreton.

Of course, no themed performance is complete without costumes. There was big hair, fedoras and jean jackets galore.

Mainstreet also worked in some theatrical aspects. This was best represented in their 90s based mashup of “Bye Bye Bye/ Baby One More Time” arranged by Mainstreet Music Director Zac Quesenberry. In this performance, the group was split into two groups based on gender. The women performed “Bye Bye Bye,” and the men performed “Baby One more Time,” in full Britney Spears attire.

While there was some elaborate choreography for some of the pieces, the overall feeling was loose and free, really allowing the performers to truly express themselves.

“This is our most dance heavy showcase we’ve ever done, but doing music from the 70s and doing disco, you can’t not move,” said Sara Chaudhary, Mainstreet marketing director.

Bas Bleu Theatre, a theater on the outskirts of Old Town, set the perfect back drop for this lively show.

“Bas Bleu really contributes to the arts community a lot, they offer all year round free spaces for groups just like us,” Quesenberry said.

The theater drew a fairly large crowd of family, friends and Mainstreet alum.

Some of the songs had a haunting beauty to them as all the voices came together to produce a powerful sound. Others had special elements unique to the group, such as the opera elements placed in the 70s hit “September.” Four of the 12 songs performed were also arranged by members of the group. Of these 12, eight are new additions to the Mainstreet repertoire.

As the show came to a close, Mainstreet decided to perform one more song as an encore, inviting Mainstreet alum in the audience, including it’s 2013 founder, up to the stage to perform the Mainstreet staple “Somewhere That we Used to Know.”

While the show was simply a show and not inherently a fundraiser, a small admission fee was requested. As Mainstreet is a group of performers, they need funds for a variety of things including travel fees to regional showcases. Also, for their most urgent need, microphones.

“We’re such a large groups there’s usually not enough microphones to accommodate us at the performances we go to,” Chaudhary said.

A vast majority of the songs were crowd pleasers and classics, allowing the audience to clap their hands and sing along.

“It’s really our most ambitious show,” Quesenberry said.

Collegian reporter Maddie Wright can be reached at entertainment@collegian.com or on Twitter @maddierwright.