When the Palo Alto Chamber Orchestra leaves for its tour of Turkey later this month, along with its precious cargo of stringed instruments it will take an unusual assortment of recent works chosen or commissioned by director Ben Simon.

Instead of focusing on Haydn or Shostakovich, the program features the music of the Americas, including Brazilian composer Ney Rosauro's Concerto for Marimba and String Orchestra, with its sultry syncopations. There's also a new atonal, somewhat minimalist work by young Berkeley composer Gabriella Smith.

The pieces, with their difficult rhythmic elements, demand a high degree of technical competence and musical literacy from PACO's 30 young musicians, most of whom have worked their way up through the five layers of PACO ensembles.

During its two-week tour, PACO will perform at the International Youth Orchestra Festival in Istanbul. The tour also includes stops in Ankara, Denizli, Izmir and Bursa.

Another challenging piece on the program is "Wadi," by 26-year-old Palo Alto composer Be'eri Moalem, who played viola and violin with the orchestra throughout his school years. The six-minute work is a musical evocation of Cairo, blasted by a chaos of sounds: the Azan call to prayer from the top of the mosque minarets, traffic noises, hooting and melodies inspired by Arabic dance. The effect is startling, with serenity dissolving into dissonance; rhythmic complexity with melodic unity; secular sounds mixed with spiritual.

"Wadi" means a deep ravine or rift, and for Moalem the name represents the gap between the Jewish-Israeli and Arabic cultures, which he feels music can help to bridge. "I remember hearing the Azan growing up in Israel but at the time I resented it — it was more of a symbol of the enemy than a religious melody," said Moalem (a former Palo Alto Weekly intern), whose family moved from Israel to Palo Alto when he was 13.

Later, he went on a solo backpacking trip that took him to Egypt and Morocco, and found the Azan beautiful. "I transcribed that and added my own ornamentation and extension," he said.

One of the main challenges was resisting the urge to harmonize. "Arabic music doesn't do that," he said. "You get complexity in other areas, in ornamentation and rhythmic complexity. But having the whole orchestra in unison is unusual in European music."

Moalem scored the piece originally for symphonic orchestra, and it was first performed by the orchestra at San Jose State University, where he is currently finishing a master's degree in composition.

Like many PACO alumni, Moalem stayed in touch with Ben Simon, returning to coach at PACO summer camps, perform occasional solos and play in the San Francisco Chamber Orchestra, which Simon also directs. From time to time, Moalem sent him pieces and Simon gave him pointers. Eventually, Simon suggested that Moalem arrange the Cairo piece for string orchestra, to be performed in Turkey as a first encore.

"It's a sort of gift to their culture," Simon said. "We're bowing to their musical custom and their religious themes. It's also interesting for our young musicians, to get a taste of definitely non-linear, non-western music."

In addition to the string orchestra, the piece is scored for guitar imitating the oud, with a string quartet replacing original scoring for wind instruments. The darbuka drum or doumbek, common in Middle Eastern music, is played by professional virtuoso percussionist Chris Froh, who is also the soloist in the Rosauro marimba concerto.

All of the works being performed are challenging, employing techniques such as glissando tremolo, and ponticello: a method of drawing the bow behind the bridge to create an unearthly scraping sound. Tom Yaron, a young PACO violinist, will employ this technique in Argentine composer Astor Piazzolla's "The Four Seasons of Buenos Aires," which features the nuevo tango rhythms for which Piazzolla is famous. Written originally for Piazzolla's own instrument, the bandoneon, this adaptation for violin and string orchestra, with marimba added for extra pizzazz, was a prime choice for Simon, who has long considered the piece "so wonderful, so cool."

Another new piece is Gabriella Smith's new composition, chosen as the winner of this year's Youth for Youth commissioning project, which Simon started several years ago. The contest invites young composers from around the country to submit compositions scored for string orchestra, and the 19-year-old Smith, who is studying at the Curtis Institute of Music in Philadelphia, entered "Light, Fog, Winds, Grasses."

The piece is a 10-minute, atonal evocation of the northern California landscape. As Smith says in her notes, it was inspired by her "love of nature as ... experienced on a bluff overlooking the Pacific." It has elements of the minimalist work of John Adams, with whom she studied in Berkeley, but is also "very personal and shows she's developing her own voice," Simon said.

Simon chose this program for the tour as something that would be "off the European-masterpiece beaten track," and that might surprise the audiences. Turkey has a rich and sophisticated classical music scene, with excellent music education that "is way beyond what we have in the United States," he said.

The fact that PACO's musicians can handle the program is testament to their years moving through the five stages of PACO orchestras, starting with SuperStrings under the direction of Kris Yenney. The 30 or so musicians going on the tour to Turkey are all from the most senior orchestra, with a few from Sinfonia (the fourth level), who auditioned to be included.

The 125 players in the five orchestras train over many years, regularly playing in large and small ensembles, and performing with outside instrumentalists and soloists. Each year, they perform in Ashland on the Shakespeare Festival's Elizabethan Theatre stage.

"It's a fairly intense experience," Simon said, adding that he is well aware of the many other demands on the younger players' time. "But we turn out well-rounded citizens, not just music jocks."

Above all, he said, camaraderie and friendships made through PACO go deep. Concert audiences are full of ex-PACO players, sometimes including youngsters who are the result of PACO marriages.

Moalem, who looks forward to joining the orchestra in Istanbul before going on to meet with other musicians in Turkey, Greece and Israel, said: "PACO is like a big family. You never really leave."

Info: For more about the Palo Alto Chamber Orchestra, go to http://pacomusic.org .