An Aeolian harp (also wind harp) is a musical instrument that is played by the wind. Named for Aeolus, the ancient Greek god of the wind, the traditional Aeolian harp is essentially a wooden box including a sounding board, with strings stretched lengthwise across two bridges. It is often placed in a slightly opened window where the wind can blow across the strings to produce sounds. The strings can be made of different materials (or thicknesses) and all be tuned to the same pitch, or identical strings can be tuned to different pitches. Besides being the only strung instrument played solely by the wind, the Aeolian harp is the only stringed instrument that plays solely harmonic frequencies.