tonic key tonic epilepsy • tonic major · · · Info · Definitions · Synonyms · Characters · · tonic key · · Text Common · · Latin · · Scripts 9 · · Length 4 · · Syllables Definitions · · · (noun) the basic key in which a piece of music is written. Synonyms: tonic key, home key. · · Noun Definition 1 Synonyms · · · home key · · Synonym 1 Characters · · space U+0020 c latin small letter c U+0063 e latin small letter e U+0065 i latin small letter i U+0069 k latin small letter k U+006B n latin small letter n U+006E o latin small letter o U+006F t latin small letter t U+0074 y latin small letter y U+0079