The Double bass, also called the string bass, contrabass, upright bass, or simply bass, is the largest and lowest-pitched bowed string instrument. It is a transposing instrument and is typically notated one octave higher than sounding to avoid excessive ledger lines.
The string is the only stringed instrument in a concert band, which is otherwise formed of only wind and percussion instruments. There is typically only one string bass per concert band, and the bassist is considered a member of the bass section.
String basses are typically found in symphony orchestras, chamber orchestras, concert bands, jazz bands, and other string ensembles.
The double bass is generally tuned in fourths, The standard tuning (low to high) is E–A–D–G, starting from E below second low C (concert pitch). This is the same as the standard tuning of a bass guitar and is one octave lower than the four lowest-pitched strings of standard guitar tuning.
As portrayed in Hibike! Euphonium
Midori "Sapphire" Kawashima is the only string bass player in the Kitauji concert band for the main anime series. In The Second Turbulent Movement Volume 1 and Hibike! Euphonium The Movie: Finale Oath, a second contrabass player, Motomi Tsukinaga, is introduced in Kumiko's second year at Kitauji High School.