As Nadia Sirota said on her great music podcast from WQXR, Meet the Composer, the Indonesian Gamelan is perhaps the most influential Eastern tradition in terms of its effect on Western music. It was introduced to most Westerners at the Paris Exhibition in 1889, where, according to Sirota, it had an intense effect on composers like Claude Debussy, Erik Satie, and later American composers like John Cage and later American Minimalists. This track is in fact a transcription of Balinese gamelan music, which is played on an instrument called a gamelan, done for two pianists by Colin McPhee and British composer Benjamin Britten.
McPhee had become enamored with the music after hearing it in New York City and moved to Bali to study it further before moving back to the US, where he lived with Britten briefly and introduced him to the Balinese tradition which had so enthralled him. Evidently Britten shared his enthusiasm, and the two recorded these transcriptions. Traditionally gamelan is performed by a group on a series of percussive xylophone- and gong-like instruments with many performers playing together (check out this video) while smaller motifs are mixed in throughout. Though it would appear to be improvised, the tunes were passed down in oral form in a precise manner. It continues to be performed in Indonesia today, and each island in the country has different forms of gamelan.