Emily Dickinson Lexicon

VOL'UN-TA-RY, n.

1. One who engages in any affair of his own free will; a volunteer. [In this sense, volunteer is now generally used.]
2. In music, a piece played by a musician extemporarily, according to his fancy. In the Philosophical Transactions, we have a method of writing voluntaries, as fast as the musician plays the notes. This is by a cylinder turtling under the keys of the organ. – Cyc.
3. A composition for the organ.