The flute is an instrument of the woodwind family.. Unlike other woodwind instruments, a flute produces its sound from the flow of air against an edge, instead of using a reed.
A flute produces sound when a stream of air directed across the top of a hole bounces in and out of the hole. Flute sounds are typically closed and hollow as a result of relatively weak upper partials. As a result, flute tones are sweet in character and blend well with other instruments.
The modern professional concert flute is generally made of silver, gold, or combinations of the two. Student instruments are usually made of nickel silver, or silver-plated brass. Wooden flutes and headjoints are more widely available than in the past.
Open hole flutes (where some keys have a hole through the middle resembling doughnuts, and whose holes the player must then cover with fingertips) are common among concert-level players, though some flautists (particularly students, but sometimes even professional flautists as well) select closed-hole "plateau" keys. Students often use temporary plugs to cover the holes in the keys until they master the more exact finger-placement that open-hole keys demand. Some people believe that open-hole keys permit louder and clearer sound projection in the flute's lower range. Open-hole keys are also needed for some modern "extended" avant garde pieces, including those requiring the player to play harmonic overtones, or to manipulate "breathy" sounds in addition to the traditional "pure" tone.