instrumental has 2 distinct synonyms spread across 1 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is vocal.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
relating to or designed for or performed on musical instruments
“instrumental compositions”
serving or acting as a means or aid
“instrumental in solving the crime”
Synonyms, antonyms and the broader and narrower relations for instrumental come from Princeton University’s WordNet. Full sources and licences.