Emily Dickinson Lexicon

key (-s), n¹. [OE cæg.] (webplay: finger's, frame, lock, played, shutting).

1. Piano component; ivory lever on the front board of an organ, pianoforte, etc.; segment of a musical instrument which the player presses down to produce musical notes; [fig.] aspect of being.
2. Fundamental note; basic tone of a piece of music; [metaphor] song; hymn; anthem.
3. Tool for release; instrument of access; mechanism for unsealing a casket; [metonymy] access; control; power of custody; admission by possession of the keys of any place.
4. Connection; emblem; symbol; sign; signal; thing that opens or closes the way to something.