ENVELOPE

in poetry, a device in which a line or a stanza is repeated so as to enclose a section of verse, as in Sir Thomas Wyat's Is it Possible?: Is it possible That so high debate, So sharp, so sore, and of such rate, Should end so soon and was begun so late? Is it possible? in musical sound, the onset, growth, duration, and decay of a sound. Growth consists of the rate of increase of a sound to steady-state intensity. Duration refers to the steady state of a sound at its maximum intensity, and decay is the rate at which it fades to silence. Envelope is an important element of timbre (q.v.), the distinctive quality, or tone colour, of a sound. Every musical instrument has its characteristic attack, growth, duration, and decay pattern.