Instrumental means playing a key part in something, or played without singing. Instrumental in the deal, an instrumental track, instrumental music.
The first sense takes in: somebody is instrumental in bringing something about, and it is a formal way of saying they made it happen. The second is plain description — an instrumental is a piece with no vocals.
1adjectiveinstrumentalPlaying a key part in something, or played without singing.
“Her letters to the council were instrumental in saving the old library.”
instrumental is a quality.
Medieval Latin instrumentalis comes from instrumentum, a tool, from instruere, to equip or arrange.
Medieval Latin
īnstrūmentālis
Middle English
instrumental
English, today
instrumental
From Middle English instrumental, instrumentale, from Medieval Latin īnstrūmentālis, equivalent to instrument + -al.
Etymology from Wiktionary, CC BY-SA