Pertaining to, made by, or prepared for, an instrument, esp. a musical instrument; as, instrumental music, distinguished from vocal music.

Without vocals

relating to or designed for or performed on musical instruments; "instrumental compositions"; "an instrumental ensemble"

Applied to a case expressing means or agency; as, the instrumental case. This is found in Sanskrit and Russian as a separate case, but in Greek it was merged into the dative, and in Latin into the ablative. In Old English it was a separate case, but has disappeared, leaving only a few anomalous forms.

Acting as an instrument; serving as a means; contributing to promote; conductive; helpful; serviceable; as, he was instrumental in conducting the business.

serving as a means, agent or tool; a key person in getting something done

serving or acting as a means or aid; "instrumental in solving the crime"

using instruments only, with no words