An aerophone (/ˈɛəroʊfoʊn/) is a musical instrument that produces sound primarily by causing a body of air to vibrate, without the use of strings or membranes (which are respectively chordophones and membranophones), and without the vibration of the instrument itself adding considerably to the sound (or idiophones). According to Sachs, These may be lips, a reed, or a sharp edge. A free aerophone lacks the enclosed column of air yet, "cause a series of condensations and rarefications by various means."