‘UD, also spelled OUD, stringed musical instrument considered "the king of instruments" by many in the Arab world, is probably the oldest and most central instrument in the Middle Eastern music tradition. It is also known as the ancestor of the European lute. Oud's name derives from al-oud or in Arabic - branch of wood. The oud has a deep, pear-shaped body and a fretless fingerboard, which allows the player to play microtonal modes or nonwestern scales. The strings are made out of gut and metal or nylon and metal, plucked with a plectrum (pick or rishy in Arabic). The rishy can be made out of plastic, deer horn or eagle feather. The strings are fastened to a tension (guitar-type) bridge on the instrument's belly. The oud has eleven strings, five pairs of strings in which each pair tuned to the same pitch, and one additional single bass string. The most common tuning, starting from the bass, is C, F, A, D, G, C, but there are other tunings that vary from country to country. The oud produces the most mellow and deep expressive sounds.