In aerophones, the sound is produced by vibrating air (usually inside the instrument). The instrument, or parts of the instrument, are shaped (often into a tube or set of tubes) so that the vibrations will be a particular length, and so a particular
pitch (see
Sound, Physics and Music .) Aerophones are grouped according to what causes the air to begin vibrating.
The melodeon, like its close relatives the accordion and the concertina, is a free-reed aerophone.
Aerophone categories
In
whistles , the air is blown at a sharp edge in the instrument (as in recorders as well as police whistles).
In
blowhole instruments, the air is blown across the sharp edge at the blowhole. When the instrument is tube-shaped, the blowhole can be in the end ("end-blown", as in panpipes), or in the side of the instrument ("side-blown", as in a fife).
In
reed instruments, the vibration of a reed or reeds begins the air vibration. In
single reed (saxophone, for example) and
double reed (oboe) instruments, the one or two reeds are part of the mouthpiece. In bagpipes and in
free-reed instruments (such as harmonica and accordion), the single or double reeds are mounted somewhere inside the instrument and there can be many of them - sometimes a different reed for every pitch.
In
cup mouthpiece instruments, the player buzzes the lips against the mouthpiece, causing a sympathetic vibration in the air inside the instrument. (bugle, conch shell).
The pipes of an
organ have a sharp edge like a whistle, but the pipes are filled with air from something other than a mouth or nose, usually a bellows of some sort.
Free aerophones (bull-roarers, toy spinning tops), cause vibrations in the air around them rather than inside them.
Membranophones
In membranophones, the sound begins with the vibration of a stretched membrane, or skin (often an actual animal skin), but the skin is usually stretched across a
resonator . Membranophones are usually classified according to the shape of the resonating body of the instrument.
Membranophones are classified by their basic shape. For example, a drum that is wider at top and bottom than in the middle is a waisted tubular drum.
Membranophone categories
Tubular drums are divided into
cylindrical ,
conical ,
barrel ,
long ,
waisted (hourglass-shaped),
goblet (with a stem at the base), and
footed (with feet around the edge of the bottom).
Kettledrums or
vessel drums have rounded bottoms.
In
frame drums , the membrane is stretched over a frame, usually making a wide, shallow instrument. (Tamborines are in this category.)
Friction drums come in a variety of shapes. Instead of beating on the membrane, the player runs a stick through a hole in the membrane.
In
mirlitons , the membrane is made to vibrate by blowing air across it. These are the only membranophones that are not drums. (Kazoos are in this category.)
Idiophones
In idiophones, it is the vibration of the instrument itself that is the main source of the musical sound. Idiophones are classified according to what you do to them to make them vibrate.
