Sound is nothing more than an audible vibration. The kind of sound you hear depends on what is vibrating.

Neal Berntsen asked a group of elementary students to put their hands to their throats while they hummed to feel the vibration of their vocal cords.

Musical instruments are grouped into families based on what vibrates on them. In woodwinds, reeds vibrate; in stringed instruments, the strings; in brass instruments, the player's lips; in percussion instruments, it's the head of the drum or a piece of metal, such as a cymbal.

Each family of instruments was highlighted by Berntsen and other members of the Pittsburgh Symphony Orchestra in a concert Tuesday morning for fourth-graders from Sharon and West Middlesex schools, and fourth- and fifth-graders at Hermitage schools.

In the afternoon, the chamber ensemble played for Hermitage seventh- and eighth-graders.

Both concerts were held in Hermitage.

Berntsen, a cornet player, and trombonist Peter Sullivan, who called his instrument "the most beautiful and perfect of all brass instruments," played the highs and lows of brass in Gerry Mulligan's jazz piece, "Line for Lyons."

Clarinetist Ron Samuels and bassoonist Philip Pandolfi played a Ludwig van Beethoven duet that featured their woodwind instruments.

Violinist Sarah O'Boyle and bassist John Moore rosined up their bows for a Franz Joseph Haydn duet.

Timothy Adams showed off the range of percussion instruments with an improvisation that featured floor tom-tom, regular and piccolo snare drums, Malaysian hand drum, triangle, and cymbals. He earned the biggest applause for a snare roll that showed his ability to play loud and soft and fast and slow.

The full ensemble played two parts of Igor Stravinsky's "L'Histoire du Soldat."

Husband-and-wife dance team Peter Kope and Michele de la Reza, co-directors of Attack Theater, touched on scientific principles to show students how they use balance and momentum to do seemingly impossible things, such as Ms. de la Reza lifting her much larger husband.

"By using momentum, a smaller body can lift a larger body," said Kope, who demonstrated what he was talking about in a performance of Astor Piazzolla's tango "Fuga y Misterio."

Many local students are introduced to instruments in fourth grade and have the opportunity to start learning to play them in fifth grade. The performers said they started playing or dancing at about that age, although Ms. O'Boyle said she was 4.

Steve Garay, band director for Hermitage schools, said he wanted students to gain an appreciation for symphonic music, instruments and the symphony.

"I hope for our students to see it takes a lot of hard work (to play an instrument) but you can come out with a wonderful product," said Rosalie Hazi, fifth-grade teacher at Delahunty Middle School, Hermitage.

Practicing was on the minds of students in their questions for the performers.

Samuels said the amount of daily practice times differ on whether there is a big concert coming up or not much going on.

"We all hope to get a couple hours a day in playing," he said.

Berntsen acknowledged that, when he was a boy, his mother had to make him practice. Now that's he's a professional, he's glad he did, he said.

"A lot of times it's fun, but sometimes it isn't," he said.

The performers were asked if they ever felt like quitting and Ms. de la Reza said there were times when she has felt burned out.

"We always take a little break and remember this is what we love to do," she said.

Michelle McBride, who teaches at West Middlesex schools, said it helps students in school when they have outside interests.

"I think it's very important to see that not only are there professional sports teams, but there are careers in other extracurricular activities that they can be involved in," she said.

Berntsen said the symphony's outreach program seeks to make students "ambassadors of music."

"We want them to feel that they can come to a concert and belong, and so there is no barrier between them and the music," he said.

Berntsen told the students they were "one of the most attentive, well-balanced audiences we've ever played before," and after the show he said he wasn't just playing them up by telling them that.

"They were fantastic. "I've never played for a better group than we had today."