n. composition (often improvised) for a solo instrument (especially solo organ) and not a regular part of a religious service or musical performance
a. of your own free will or design; done by choice; not forced or compelled
a. controlled by individual volition
a. 自动的, 自愿的, 故意的, 志愿的, 自发的
n. 自愿行动, 志愿者, 自由调