History

History
Serpent → ophicleide → euphonion → saxhorn → the modern horn: how the tenor voice of the low brass took its present shape in barely a century.
What was the serpent
The serpent was a curved wooden bass wind instrument played with a cup mouthpiece and finger holes. From the late 16th century it supported church voices, then entered bands and orchestras before the ophicleide and valved low brass displaced it.
When was the compensating system invented
David Blaikley of Boosey & Co. is credited with the compensating system in 1874. The principle arrived then; the familiar four-valve 3+1 euphonium and its modern manufacture developed over the decades that followed.
Who invented the euphonium
There's no single inventor. The euphonium emerged in the 1840s–50s from several makers experimenting with wide-bore valved brass; Ferdinand Sommer and Adolphe Sax are both part of the story, and the modern instrument was shaped later by the compensating system.
What was the ophicleide
A keyed brass bass instrument of the early 19th century — essentially a brass instrument with woodwind-style keys covering tone holes. It bridged the serpent and the valved euphonium and tuba, then was made obsolete by them.
Why do Americans call it a baritone
American school-band tradition absorbed the euphonium under the looser label 'baritone,' partly from earlier smaller-bore instruments and partly from the manufacturing and pedagogy of US school bands. The instrument is usually a euphonium regardless of the name on the case.
Is a euphonium a saxhorn
Historically yes — the euphonium descends from the B♭ saxhorn family patented by Adolphe Sax in the 1840s. Whether today's wide-bore euphonium still counts as a 'saxhorn' is a matter of how strictly you draw the family line.