voluntary

Done or undertaken of one’s own free will.

Acting or done willingly and without constraint or expectation of reward.

Normally controlled by or subject to individual volition.

Capable of making choices; having the faculty of will.

Supported by contributions or charitable donations rather than by government appropriations.

Without legal obligation or consideration.

Done intentionally but without premeditation or deliberation, as when under the influence of an intense emotional reaction.

A short piece of music, often improvised on a solo instrument, played as an introduction to a larger work.