Wiktionary
upright bass
n. (context musical instrument English) double bass (gloss: lowest-pitched of instruments of violin family)
Usage examples of "upright bass".
The leader played a kind of accordion with nothing but buttons on it, called a bandoneon, and his companions played violin, guitar, piano, and an upright bass.
As it grew, he thought it was the overtone of a note from an upright bass, hanging in the air after the note itself had faded—.