to extemporize, ad lib, play it by ear, take it as it comes, make it up as you go along

Simply put, to improvise is to make something up on the spur of the moment. That something could be just about anything from a song, to a cake, to a headdress, to a lie. When you improvise, you invent something, which usually results in new patterns or ways of acting.

The word or the act of improvisation can "apply to various forms of communication and expression across all artistic, scientific, physical, cognitive, academic, and non-academic disciplines" (from Wikipedia, the free encyclopedia).

We frequently see examples of it watching the media, when news reporters improvise, especially if something goes wrong or they lose their place or train of thought. It happens when persons are up in front of an audience; such as professional speakers, presenters and stand up comics, for example. Improvisation is commonly used in performing arts such as jazz, dance, theater and film.

Improvisation has been strongly present in both vocal and instrumental music since the early troubadours and minstrels roamed the countryside making up all kinds of ditties to sing to the listening country folk. As music progressed and became more "refined" it found its way into the drawing rooms of the elite. Musicians and composers like Mozart, Beethoven, Listz, and Chopin, among others, all improvised at the piano for enjoyment, to entertain, and as they invented new pieces of music. Improvisation has been commonly defined as "composing music while playing an instrument at the same time." The well-know Baroque composer, Johann Sebastian Bach, was a master at creating (improvising) "variations" on specific themes.

Music improvisers often understand the idiom of one or more musical styles—e.g. blues, rock, folk, jazz—and work within that idiom to express ideas with creativity and originality. Improvisation can take place as a solo performance, or interdependently in ensemble with other players. Some of the greats in jazz are Miles Davis, innovative trumpet player known for his spare style, John Coltrane, unparalleled saxophonist, Charles Mingus, extremely imaginative bassist and composer, Bill Evans, the revolutionary pianist heavily influenced by Ravel and Debussy, and Sarah Vaughan and Ella Fitzgerald, both accomplished jazz singers, to name only a few. Musicians and singers of other styles, who have mastered the skill of improvisation, are too numerous to mention here.

Dance
When choreographers set their dance creations to music or create a dance performance on stage, they utilize the shape and space of that stage or area to create moves within a certain allotted time, with or without music. As they begin their creation, the improvised dance is affected by the amount of given space, the energy of the dancers and the various moves the bodies of the dancers are capable of making, often juxtaposing two or more dancers in imaginative ways. A form of dance improvisation referred to as "contact improvisation, originated by Steve Paxton in the 1970s is based on sharing weight, partnering, playing with weight and unpredictable outcomes. Martha Graham and more recently Twyla Tharp have used innovative improvisation extensively in their choreographed pieces.

Also known as "Improv", improvisational theater is a form of theater in which actors use improvisational techniques to perform spontaneously. It allows for an interactive relationship with the audience and is unscripted. There are no props, in fact most improvisers would rather not use props in favor of using mime. Improvisers typically use audience suggestions to guide the performance as they create dialogue setting, and plot. These performances tend to be comedic, although some forms are not necessarily so. Many improvisational actors/ improvisers also work as scripted actors, and "improv" techniques are often taught in standard acting classes. The basic skills of listening, clarity, confidence, and performing instinctively and spontaneously are considered important skills for improv actors to develop. A few well known actors who are brilliant improvisers are: Robin Williams, Steve Carrell, and Bill Murray.

There are many improv theaters through the united states and Canada. One of the most well known, Second City, is in Chicago and also in Toronto. Many of the original cast of Saturday Night Live came from Second City and the franchise has produced such comedy stars as Mike Myers, Chris Farley and John Belushi The Chicago theater has turned out improvisational comedians and actors such as Alan Arkin, Bonnie Hunt, Tina Fey, Bill Murray, and Gilda Radner, to name a few. Second City was begun by Viola Spolin, a pioneer in the field. She first wrote the book "Theater Games", a handbook for students of improv, filled with games and techniques for developing the skill. A second book, "Improvisation for the Theater", is still popular. "The Second City Almanac of Improvisation, a recent publication edited by Anne Libera, is a collection of diverse ideas, viewpoints, and memories by teachers, actors and directors who all got their start in comedy theater.

There are many different ways of using improvisation in film and directors have always allowed gifted actors to do so, if it enhances the script or the experience. It is more prevalent today than ever. Mike Leigh (of the London theater) uses lengthy improvisations developed over a period of weeks to build characters and story lines for his films. Judd Apatow, writer-producer-director, well known for his comic films (eg: 40 year Old Virgin" and "Knocked Up") allows his actors great leeway with their scripts. Directors Michael Mann and Christopher Guest both use improvisation to gain strong performances from their cast.

Sitcoms and game shows

In the 1990s, a TV show called Whose line is it anyway? popularized comedic improvisation in England. It was popularized in the US by Drew Cary, who was the host. More recently, HBO's Curb your enthusiasm with Jerry Seinfeld and the Bravo series Significant Others have used improvisation to create longer programs with a dramatic edge. Most game show hosts and sitcom actors are quite adept at improvising. And, it'd fun to try to figure out when those moments occur. You can usually tell by the reactions of the other actors when something unexpected is said.

Talk Shows
Talk show hosts, like Ellen DeGeneres, Jay Leno, Dave Letterman, Carson Daly, and Rosie ODonnell are famous for their ability to improvise. Many have been trained in improv theater and are comedians and actors as well. They all know how to deliver a good punch line.

Reality TV
A fairly new genre of improvisational theater is Reality TV. Most of these shows have some kind of script to follow loosely and I would surmise there is a lot of editing going on, after the fact; but much of these shows is improvised, with many captured moments, the actors may or may not be aware of. The editing is usually done to achieve certain story lines, attitudes, and emotional contrivances.