Improvisation is the practice of acting, singing, talking and reacting, of making and creating, in the moment and in response to the stimulus of one's immediate environment and inner feelings. This can result in the invention of new thought patterns, new practices, new structures or symbols, and/or new ways to act. This invention cycle occurs most effectively when the practitioner has a thorough intuitive and technical understanding of the necessary skills and concerns within the improvised domain. Improvisation can be thought of as an "on the spot" or "off the cuff" spontaneous activity.
Musical improvisation (also known as musical extemporization) is the creative activity of immediate ("in the moment") musical composition, which combines performance with communication of emotions and instrumental technique as well as spontaneous response to other musicians. In other words, the art of improvisation can be understood as composing music "on the fly." This requires great skill and knowledge, and is a very important aspect of music in general. Musical improvisers often understand the idiom of one or more musical styles — such as blues, rock, folk, jazz — and work within the idiom and music-theory of the certain style to express ideas with creativity and originality.
Throughout the Medieval, Renaissance, Baroque, Classical, and Romantic periods, improvisation was a highly valued skill. It is also common in non-Western musical traditions, such as Indian classical music and Persian traditional music. An interesting example of improvisation is found in the realm of silent film music, where musicians have to match the style and pacing of the films they accompany, often at first sight, which demands a knowledge of a wide range of musical styles as well as the stamina to play for films which occasionally run over three hours in length without a pause. Contemporary improvisation is particularly common in jazz, contemporary classical music, and jam bands. However, improvisation can be performed in nearly any genre of music. Rap battles, extended guitar solos, and Live PA sets could all be considered forms of improvisation. .