Instrumental (adjective)

1. Serving as an important means or tool in achieving a result or an end.
2. Being essential or necessary for a particular purpose or activity.
3. Relating to or denoting music that is performed with musical instruments, as opposed to music performed by the human voice.

Origin:

From the late middle english instrumental, from latin instrumentalis, from instrumentum meaning tools or implements. first used in the 15th century.

Examples:

1. He was instrumental in developing the new program.
2. Her work was instrumental in the success of the project.
3. The instrumental music was playing in the background.
4. His leadership was instrumental in winning the war.
5. This report is instrumental in guiding our future decisions.