The serpent is a bass wind instrument that looks like a long, snaking wooden tube covered in black leather. It was invented in the late 16th century, likely by Edmé Guillaume, to support the bass voices of church choirs. Although made of wood, it is considered a brass ancestor because it uses a cup-shaped mouthpiece and the player's lips vibrate to produce sound. It has finger holes like a woodwind, which the player uses to change pitch. The serpent has a unique, mellow, but somewhat unstable tone. It was used in orchestras until the mid-19th century, famously appearing in scores by Mendelssohn and Wagner before being replaced by the more reliable ophicleide and eventually the tuba. Playing the serpent is notoriously difficult because the finger holes are spaced far apart and the intonation is very sensitive to the player's breath and lip tension.