An oboe is a woodwind instrument with a double reed. It looks very similar to the clarinet, and may be confused with it. While the clarinet's shape remains cylindrical, the oboe's body is conical. The sounds produced by clarinets and oboes are very different. An oboe's sound is produced by blowing air through the double reed at the upper end of the instrument which forces the two reeds to vibrate together which produces the sound. The oboe has four parts: the bell, lower joint, upper joint, and the reed. A person that plays the oboe is called an oboist. A typical orchestra may have two oboes but sometimes three. Sometimes there is also a cor anglais which sounds a fifth lower than the oboe. Very occasionally there is also a bass oboe, which sounds an octave below the oboe. Gustav Holst used one in his Suite "The Planets".