Double bass
Throughout classical repertoire, there are notes that fall below the range of a standard double bass. Notes below low E appear regularly in double bass parts in the Baroque and Classical eras, when the double bass was typically doubling the cello part an octave below. In the Romantic era and the 20th-century, composers such as Mahler, Beethoven, Busoni, and Prokofiev also requested notes below the low E. There are two common methods for making these notes available to the player. Major European orchestras generally use basses with a fifth string, tuned to B three octaves and a semitone below middle C. Players with standard double basses (E-A-D-G) typically play the notes below "E" an octave higher.