Clarissa Boden plays several instruments, but her favorite one to play for audiences is the glass harp.

She also plays the piano, organ and Irish tin whistle.

“The glass harp is a really unique instrument and it's great to see people's expressions after I play it,” said Boden, 29, of Oklahoma City, Okla., formerly of Butler.

She will perform with her glass harp at 3 p.m. Sunday at Heinz Memorial Chapel in Pittsburgh. Admission is free.

Boden has been playing the unusual instrument for 12 years now.

“I saw someone else playing it, and he explained the basics of how it worked,” Boden said. “I listened to what he said, and I went from there.”

First she had to build a glass harp of her own.

“It was a lot of trial and error,” she said.

“The one I have now I made in 2008. I had a smaller set which I had made as well before that.”

She constructed them from wood blocks covered with fabric and regular stemmed drinkware from thrift stores.

“It's a misconception that the glass has to be crystal to play. That's not true,” Boden said.

Music is made by rubbing the rims of the glasses with wet fingers.

“By rubbing it, you cause friction and that causes the glass to vibrate,” Boden said.

A louder sound is produced by pressing harder or going around the rim faster, she said.

Some of the glasses on her harp are fine glass and some are not, she said.

Just to be sure about their sound, she tried the glasses out in the store.

She admitted, “I got strange looks but that's what I did!”

Her first harp had 15 glasses and the current set has 32, she said. She also has two extra glasses just for dipping her fingers.

The amount of water filled to a Sharpie line on the outside of the glass makes the specific note.

“Each glass is marked so I fill the glass to there and then I have to fine tune it” with an electronic tuner, Boden said.

“The tuner just says whether the note is sharp or flat and I tune (the glass) from there” by adjusting the amount of water, she said.

The glasses are arranged in a progression of notes. They're set up in rows of three, all at the same height, and every note is represented.

She said she has about a dozen spare glasses just in case one breaks.

For transporting, the 2-foot by 4-foot instrument fits in the back of her car with the seats down. “There's a lid that goes over the top to protect the glass,” she said.

Boden has played for senior citizens groups, Christmas concerts and churches, among other groups.

The Heinz Chapel concert is her biggest venue yet.

On Sunday, she will present a selection of sacred and traditional music as well as explain the history and workings of the glass harp.

The home-schooled student is the daughter of Timothy and Cynthia Boden of Butler.