A contrabass is the very big string instrument that stands on the floor in an orchestra. Most English speakers call it a double bass; contrabass is the same instrument, just a more formal or classical name. It plays the lowest string notes you usually hear. The player either stands or sits on a high stool, and the sound is deep and round, not sharp. You will also meet contrabass as a label on other instruments (a contrabass clarinet, a contrabassoon), where it means “an octave lower than the ordinary bass one” — though the word on its own, as a noun, is the double bass.

低音提琴（和 double bass 是同一種樂器；音樂圈較常說這個較正式的名字）