Over the last half a dozen years, Yitzhak Yedid has built a reputation for writing and performing challenging music that combines improvisation and contemporary classical music. During that period, Yedid has performed around the globe and produced five CDs. His ethnic roots sometimes get the better of him, and the Jerusalemite pianist of Iraqi and Syrian descent happily strays into wild and woolly cultural terrain, even if it's not quite his own. This Thursday, Yedid will perform in an intriguing concert at Jerusalem's Confederation House, with further performances set for Tel Aviv and Haifa the following week. Yedid will perform together with a culturally diverse ensemble that goes by the name of Ras Desehen. Yedid will play with double bass player Ora Boasson-Horev and Italian-born singer/percussionist Esti Keinan-Ofri, as well as saxophonist/vocalist Abatte Barihon, percussionist Tagan Zaneba and dancer Tizetah, all of whom were born in Ethiopia. Beyond the performers' backgrounds, Yedid and his cohorts draw on an even wider variety of musical genres. Roughly 20 years ago, Keinan-Ofri was a member of jazz trio Tzilil Shakhen, while Abatte originally earned a living as a jazz blues artist, regularly touring Europe before moving to Israel in 1999. Boasson-Horev is a classical musician, albeit with a highly contemporary style, while Zaneba adds richly textured African rhythms and colors. It is a mix which Yedid believes will yield even more than the sum of its variegated parts. "In a way, this is a continuation of the original Ras Deshen band," said Yedid, referring to his collaboration with Abatte a couple of years ago, "but there are a few additions." The Ras Deshen synergy, which can be enjoyed on an eponymously-titled CD subtitled "from Ethiopian music to contemporary jazz," explored various strains of Ethiopian liturgical music and jazz and blues straight from Africa, rather than the better known blues variety that reached western ears via New Orleans and the Delta region of the southern United States. The "additions" to which Yedid refers are compositions by Abatte and Keinan-Ofri. Keinan-Ofri came up with the idea for the current project. "Esti suggested we do something based on songs and prayers sung by kessim (Ethiopian priests)," explains Yedid. "We have added new material to the first Ras Deshen program (named after the highest mountain in Ethiopia, which is of great local spiritual importance) and there are new arrangements." Meanwhile, Yedid got on with his homework. "I went to the National Library and found some recordings by kessim. There were Shabbat songs and tehillim put to music," he said. Abatte had his own homegrown input to offer, and the combined effort spawned this week's Mizmorei Tehillim (Psalm Songs) concert. But according to Yedid, there are other cross-cultural and even sociological designs behind the Mizmorei Tehillim project. "The idea of the concert is to marry Ethiopian folk and liturgical music with Israeli material, with some jazz and ethnic things. There is a message in there, to show how the Ethiopians have found their place in Israeli society," he said. While Yedid, Abatte and Keinan-Ofri have laid the groundwork for the concert with great professionalism and attention to detail, the show itself should be far from clinical. "We also sing some a cappella parts, like Ethiopian folk music. But it's not like classical music. It's not meant to be so precise, or operatic," he said. With their rich and varied training and experience, you couldn't really expect anything too mundane from the Yedid, Abatte and Keinan-Ofri triumvirate. "Esti took music by kessim and changed the rhythms, and took the pentatonic scales forward and developed them. It's a bit more sophisticated." Naturally, of the three, it is Abatte who has the most traditional take on the music. Anyone who has caught Abate's concerts over the last three or four years has marveled at the captivating, plaintive power of his grassroots blues vocals. Two of Abatte's three compositions will be visually enhanced by Tizetah's choreography. "Dance is a very important part of Ethiopian life," says Yedid. "They even dance at funerals." The fruits of these different cultural and musical influenced might have produced a pretentious and dissonant hodgepodge that strived but failed to find a comfortable common ground. But Yedid made sure all that roads led to Addis Ababa and Jerusalem. "I made a suite out of all the compositions, with room for some improvisation," he said. "In the end there is a story to be told." Ras Deshen will perform Mizmorei Tehillim at Confederation House in Jerusalem December 22 at 8:30 p.m.; at Tzavta in Tel Aviv on Dec. 24 at 9 p.m.; and at the Tikotin Museum in Haifa on Dec. 29 at 8:30 p.m.