The Great Highland Bagpipe (Gaelic : A' Phìob Mhòr, in
English often abbreviated GHB) is a type of bagpipe native to Scotland.
It has achieved widespread recognition through its usage in the British
military and in pipe bands throughout the world.
The bagpipe is first attested in Scotland around 1400 A.D., having
previously appeared in European artwork in Spain in the 1200s. The
earliest references to Scottish bagpipes are in a military context, and
it is in that context that the Great Highland Bagpipe became established
in the British military and achieved the widespread prominence it enjoys
today, whereas other bagpipe traditions throughout Europe, ranging from
Spain to Russia, almost universally went into decline by the late 19th
and early 20th centuries.
Though widely famous for its role in military and civilian pipe bands,
the Great Highland Bagpipe is also used for a solo virtuosic style
called piobaireachd (aka pibroch).

Though popular belief sets varying dates for the
introduction of bagpipes to Scotland, concrete evidence is limited until
approximately the 15th Century. The Clan Menzies still owns a remnant of
a set of bagpipes said to have been carried at the Battle of Bannockburn
in 1314, though the veracity of this claim is debated. There are many
ancient legends and stories about bagpipes which were passed down
through minstrels and oral tradition, whose origins are now lost.
However, textual evidence for Scottish bagpipes is more definite in
1396, when records of the Battle of the North Inch of Perth reference "warpipes"
being carried into battle. These references may be considered evidence
as to the existence of particularly Scottish bagpipes, but evidence of a
form peculiar to the Highlands appears in a poem written in 1598 (and
later published in The Complaynt of Scotland which refers to several
types of pipe, including the Highland: "On hieland pipes, Scotte and
Hybernicke / Let heir be shraichs of deadlie clarions."
The Great Highland Bagpipe is classified as a woodwind
instrument, like the bassoon, oboe, or clarinet. Although it is
classified as a double reed instrument, the reeds are all closed inside
the wooden stocks, instead of being played directly by mouth as other
woodwinds are. The GHB actually has four reeds; the chanter reed
(double), two tenor drone reeds (single), and one bass drone reed
(single).
A modern set has a bag, a chanter, a blowpipe, two tenor drones, and one
bass drone. The scale on the chanter is in Mixolydian mode, which has a
flattened 7th or leading tone. It has a range from one whole tone lower
than the tonic to one octave above it (in piper's parlance: Low G, Low
A, B, C#, D, E, F#, High G, and High A; the C and F could or should be
called sharp but this is often omitted).* Yet the notes played are
actually in the key of B♭. Although less so now, depending on the tuning
of the player, certain notes are tuned slightly off just intonation, for
example, the D could be tuned slightly sharp for effect. However, today
the notes of the chanter are usually tuned in just intonation to the
Mixolydian scale. The two tenor drones are an octave below the keynote
(Low A) of the chanter) and the bass drone two octaves below.
Modern developments have included reliable synthetic drone reeds, and
synthetic bags that deal with moisture arguably better than hide bags.
Text courtesy Wikipedia