Improvise

To compose, recite, or sing extemporaneously, especially in verse; to extemporize; also, to play upon an instrument, or to act, extemporaneously.

To bring about, arrange, or make, on a sudden, or without previous preparation.

To invent, or provide, offhand, or on the spur of the moment; as, he improvised a hammer out of a stone.

To produce or render extemporaneous compositions, especially in verse or in music, without previous preparation; hence, to do anything offhand.