In its most basic form, a flute is an open tube which is blown into. After focused study and training, players use controlled air-direction to create an airstream in which the air is aimed downward into the tone hole of the flute's headjoint. There are several broad classes of flutes. With most flutes, the musician blows directly across the edge of the mouthpiece, with 1/4 of their bottom lip covering the embouchure hole. However, some flutes, such as the whistle, gemshorn, flageolet, recorder, tin whistle, tonette, fujara, and ocarina have a duct that directs the air onto the edge (an arrangement that is termed a "fipple"). These are known as fipple flutes. The fipple gives the instrument a distinct timbre which is different from non-fipple flutes and makes the instrument easier to play, but takes a degree of control away from the musician.