Improvisational theatre , often called improv or impro , is the form of theatre, often comedy, in which most or all of what is performed is unplanned or unscripted: created spontaneously by the performers. In its purest form, the dialogue, action, story, and characters are created collaboratively by the players as the improvisation unfolds in present time, without use of an already prepared, written script. It is most commonly used when an individual forgets his script.
Improvisational theatre exists in performance as a range of styles of improvisational comedy as well as some non-comedic theatrical performances. It is sometimes used in film and television, both to develop characters and scripts and occasionally as part of the final product.
Improvisational techniques are often used extensively in drama programs to train actors for stage, film, and television and can be an important part of the rehearsal process. However, the skills and processes of improvisation are also used outside the context of performing arts - Applied Improvisation. It is used in classrooms as an educational tool and in businesses as a way to develop communication skills, creative problem solving, and supportive team-work abilities that are used by improvisational, ensemble players. It is sometimes used in psychotherapy as a tool to gain insight into a person's thoughts, feelings, and relationships.
The earliest well documented use of improvisational theatre in Western history is found in the Atellan Farce of 391 BC. From the 16th to the 18th centuries, commedia dell'arte performers improvised based on a broad outline in the streets of Italy. In the 1890s, theatrical theorists and directors such as the Russian Konstantin Stanislavski and the French Jacques Copeau, founders of two major streams of acting theory, both heavily utilized improvisation in acting training and rehearsal.
Modern theatrical improvisation games began as drama exercises for children, which were a staple of drama education in the early 20th century thanks in part to the progressive education movement initiated by John Dewey in 1916.  Some people credit American Dudley Riggs as the first vaudevillian to use audience suggestions to create improvised sketches on stage. Improvisation exercises were developed further by Viola Spolin in the 1940s, 50s, and 60s, and codified in her book Improvisation For The Theater , the first book that gave specific techniques for learning to do and teach improvisational theater. In the 1970s in Canada, British playwright and director Keith Johnstone wrote Impro: Improvisation and the Theatre , a book outlining his ideas on improvisation, and invented Theatresports, which has become a staple of modern improvisational comedy and is the inspiration for the popular television show Whose Line Is It Anyway?
Spolin influenced the first generation of modern American improvisers at The Compass Players in Chicago, which led to The Second City. Her son, Paul Sills, along with David Shepherd, started The Compass Players. Following the demise of the Compass Players, Paul Sills began The Second City. They were the first organized troupes in Chicago, and the modern Chicago improvisational comedy movement grew from their success.
Many of the current "rules" of comedic improv were first formalized in Chicago in the late 1950s and early 1960s, initially among The Compass Players troupe, which was directed by Paul Sills. From most accounts, David Shepherd provided the philosophical vision of the Compass Players, while Elaine May was central to the development of the premises for its improvisations. Mike Nichols, Ted Flicker, and Del Close were her most frequent collaborators in this regard. When The Second City opened its doors on December 16, 1959, directed by Paul Sills, his mother Viola Spolin began training new improvisers through a series of classes and exercises which became the cornerstone of modern improv training. By the mid-1960s, Viola Spolin's classes were handed over to her protégé, Jo Forsberg, who further developed Spolin's methods into a one-year course, which eventually became The Players Workshop, the first official school of improvisation in the USA. During this time, Forsberg trained many of the performers who went on to star on The Second City stage.
Many of the original cast of Saturday Night Live came from The Second City, and the franchise has produced such comedy stars as Mike Myers, Tina Fey, Bob Odenkirk, Amy Sedaris, Stephen Colbert, Eugene Levy, Jack McBrayer, Steve Carell, Chris Farley, Dan Aykroyd, and John Belushi.
Simultaneously, Keith Johnstone's group The Theatre Machine, which originated in London, was touring Europe. This work gave birth to Theatresports, at first secretly in Johnstone's workshops, and eventually in public when he moved to Canada. Toronto has been home to a rich improv tradition.
In 1984, Dick Chudnow (Kentucky Fried Theater) founded ComedySportz in Milwaukee, WI. Expansion began with the addition of ComedySportz-Madison (WI), in 1985. The first Comedy League of America National Tournament was held in 1988, with 10 teams participating. The league is now known as World Comedy League and boasts a roster of 24 international cities.
In San Francisco, The Committee theater was active in North Beach during the 1960s. It was founded by alumni of Chicago's Second City, Alan Myerson and his wife Jessica. When The Committee disbanded in 1972, three major companies were formed: The Pitchell Players, The Wing, and Improvisation Inc. The only company that continued to perform Close's Harold was the latter one. Its two former members, Michael Bossier and John Elk, formed Spaghetti Jam in San Francisco's Old Spaghetti Factory in 1976, where shortform improv and Harolds were performed through 1983. Stand-up comedians performing down the street at the Intersection for the Arts would drop by and sit in. In 1979, Elk brought shortform to England, teaching workshops at Jacksons Lane Theatre, and he was the first American to perform at The Comedy Store, London, above a Soho strip club.
Modern political improvisation's roots include Jerzy Grotowski's work in Poland during the late 1950s and early 1960s, Peter Brook's "happenings" in England during the late 1960s, Augusto Boal's "Forum Theatre" in South America in the early 1970s, and San Francisco's The Diggers' work in the 1960s. Some of this work led to pure improvisational performance styles, while others simply added to the theatrical vocabulary and were, on the whole, avant-garde experiments.
Joan Littlewood, an English actress and director who was active from the 1930s to 1970s, made extensive use of improv in developing plays for performance. However, she was successfully prosecuted twice for allowing her actors to improvise in performance. Until 1968, British law required scripts to be approved by the Lord Chamberlain's Office. The department also sent inspectors to some performances to check that the approved script was performed exactly as approved.
In 2012, Lebanese writer and director Lucien Bourjeily used improvisational theater techniques to create a multi-sensory play entitled 66 Minutes in Damascus . This play premiered at the London International Festival of Theater, and is considered one of the most extreme kinds of interactive improvised theater put on stage. The audience play the part of kidnapped tourists in today's Syria in a hyperreal sensory environment. 
Rob Wittig and Mark C. Marino have developed a form of improv for online theatrical improvisation called netprov.  The form relies on social media to engage audiences in the creation of dynamic fictional scenarios that evolve in real-time.
Modern improvisational comedy, as it is practiced in the West, falls generally into two categories: shortform and longform.
Shortform improv consists of short scenes usually constructed from a predetermined game, structure, or idea and driven by an audience suggestion. Many shortform exercises were first created by Viola Spolin, who called them theater games, influenced by her training from recreational games expert Neva Boyd. The shortform improv comedy television series Whose Line Is It Anyway? has familiarized American and British viewers with shortform.
Longform improv performers create shows in which short scenes are often interrelated by story, characters, or themes. Longform shows may take the form of an existing type of theatre, for example a full-length play or Broadway -style musical such as Spontaneous Broadway. One of the better-known longform structures is the Harold, developed by ImprovOlympic co-founder Del Close. Many such longform structures now exist. Longform improvisation is especially performed in Chicago, New York City, Los Angeles ; has a strong presence in Austin, Boston, Minneapolis, Phoenix, Philadelphia, San Francisco, Seattle, Detroit, Toronto, Vancouver, Washington, D.C. ; and is building a growing following in Denver, Montreal, Kansas City, Columbus, New Orleans, Omaha, Rochester,  and Hawaii. Outside the United States, longform improv has a growing presence in the United Kingdom, especially in cities such as London, Bristol, and at the Edinburgh Festival Fringe.
Some principles of improv
There are no absolute rules in improv but here are some principles.
- Listen: easier said than done, and that's exactly the point
- Agreement: say yes and add something, don't reject ideas
- Team Work: have a group mind, think of others
- Don't Block: stealing jokes / not listening / changing topic
- Relationship: focus on connection between characters, not just subject of scene
- Initiation: who, what, when to set the scene
- Point of View, Opinion and Intention: have them, these help express and build your character
- Be in Character: maintain character throughout the scene
- Don't Ask Questions: too many questions can make your partner do all the work
- Make Active Choices: Do something. Don't be talking heads
- Yes, And: Take what your scene partner gives you, acknowledge it, and build off of that idea
Examples of improv comedy games
There are several types of improv comedy games that follow these general principles of improv: Improv games are fun to make up and can be experimental. Games can be adapted to tell a different story with the same or similar triggers.
Good Cop Bad Cop
Players : (3) good cop, bad cop, the criminal
How to play: The game begins with the criminal leaving the room - before any of the callouts are taken. Once out of sounds reach, the host asks the audience 3 questions to establish why the person was arrested.
1) What crime did they commit?
2) Where did they commit the crime?
3) With whom did they commit the crime?
The prisoner is brought into the holding cell (stage) by one of the cops. The cops interrogate the prisoner in their personas as good cop (gives the prisoner a break, not as aggressive) and bad cop (forceful, doubts prisoner). Through this back and forth between the prisoner and the cops the prisoner tries to answer the 3 questions above - in this order. Once the prisoner solves all 3, they must write a confession. "I stole a goat from my neighbors closet with Jimmy Fallon."
I Once Dated A ...
Players : All + host
How to play: all the players line up shoulder to shoulder on the stage with one microphone in the center (you can play without a mic too). The host has a list of objects from the audience (distribute paper and pens before the performance to get call outs for games like this). The host begins the game by picking an object from the audience's list and prompts the players by saying, "I once dated an octopus" (repeats it again for clarity). Each player - not necessarily in order - step up to the mic and finish the statement. "I once dated an octopus. It was always awkward when we went out for sushi." After this, either another player goes forward with another idea or the host calls out another object.
Non-comedic, experimental, and dramatic, narrative-based improvisational theater
Other forms of improvisational theatre training and performance techniques are experimental and avant-garde in nature and not necessarily intended to be comedic. These include Playback Theatre and Theatre of the Oppressed, the Poor Theatre, the Open Theatre, to name only a few.
The Open Theatre was founded in New York City by a group of former students of acting teacher Nola Chilton, and joined shortly thereafter by director Joseph Chaikin, formerly of The Living Theatre, and Peter Feldman. This avante-garde theatre group explored political, artistic, and social issues. The company, developing work through an improvisational process drawn from Chilton and Viola Spolin, created well-known exercises, such as "sound and movement" and "transformations", and originated radical forms and techniques that anticipated or were contemporaneous with Jerzy Grotowski's " poor theater " in Poland. During the sixties Chaikin and the Open Theatre developed full theatrical productions with nothing but the actors, a few chairs and a bare stage, creating character, time and place through a series of transformations the actors physicalized and discovered through improvisations.
Longform, dramatic, and narrative-based improvisation is well-established on the west coast with companies such as San Francisco's BATS Improv. This format allows for full-length plays and musicals to be created improvisationally.
Applying improv principles in life
Many people who have studied improv have noted that the guiding principles of improv are useful, not just on stage, but in everyday life.  For example, Stephen Colbert in a commencement address said, 
Well, you are about to start the greatest improvisation of all. With no script. No idea what's going to happen, often with people and places you have never seen before. And you are not in control. So say "yes." And if you're lucky, you'll find people who will say "yes" back.
Tina Fey in her book Bossypants lists several rules of improv that apply in the workplace.  There has been much interest in bringing lessons from improv into the corporate world. In a New York Times article titled , Stanford professor and author, Patricia Ryan Madson notes, "executives and engineers and people in transition are looking for support in saying yes to their own voice. Often, the systems we put in place to keep us secure are keeping us from our more creative selves."
In film and television
Many directors have made use of improvisation in the creation of both mainstream and experimental films. Many silent filmmakers such as Charlie Chaplin and Buster Keaton used improvisation in the making of their films, developing their gags while filming and altering the plot to fit. The Marx Brothers were notorious for deviating from the script they were given, their ad libs often becoming part of the standard routine and making their way into their films. Many people, however, make a distinction between ad-libbing and improvising. 
The British director Mike Leigh makes extensive use of improvisation in the creation of his films, including improvising important moments in the characters' lives that will not even appear in the film. This Is Spinal Tap and other mockumentary films of director Christopher Guest are created with a mix of scripted and unscripted material and Blue in the Face is a 1995 comedy directed by Wayne Wang and Paul Auster created in part by the improvisations during the filming of Smoke .
Improv comedy techniques have also been used in television and stand-up comedy in hit shows such as HBO's television show Curb Your Enthusiasm created by Larry David, the UK Channel 4 and ABC television series Whose Line Is It Anyway (and its spinoffs Drew Carey's Green Screen Show and Drew Carey's Improv-A-Ganza ), Nick Cannon's improv comedy show Wild 'N Out , and Thank God You're Here . In Canada, the series Train 48 was improvised from scripts which contained a minimal outline of each scene, and the comedy series This Sitcom Is...Not to Be Repeated incorporated dialogue drawn from a hat during the course of an episode. The American show Reno 911! also contained improvised dialogue based on a plot outline. Fast and Loose is an improvisational game show, much like Whose Line Is It Anyway? . The BBC sitcoms Outnumbered  and The Thick of It also had some improvised elements in them.
In the field of the psychology of consciousness, Eberhard Scheiffele explored the altered state of consciousness experienced by actors and improvisers in his scholarly paper Acting: an altered state of consciousness .  According to G. William Farthing in The Psychology of Consciousness comparative study, actors routinely enter into an altered state of consciousness (ASC).  Acting is seen as altering most of the 14 dimensions of changed subjective experience which characterize ASCs according to Farthing, namely: attention, perception, imagery and fantasy, inner speech, memory, higher-level thought processes, meaning or significance of experiences, time experience, emotional feeling and expression, level of arousal, self-control, suggestibility, body image, and sense of personal identity.
In the growing field of Drama Therapy, psychodramatic improvisation, along with other techniques developed for Drama Therapy, are used extensively. The "Yes, and" rule has been compared to Milton Erickson's utilization process and to a variety of acceptance-based psychotherapies. Improv training has been recommended for couples therapy and therapist training, and it has been speculated that improv training may be helpful in some cases of social anxiety disorder. 
Structure and process
Improvisational theatre often allows an interactive relationship with the audience. Improv groups frequently solicit suggestions from the audience as a source of inspiration, a way of getting the audience involved, and as a means of proving that the performance is not scripted. That charge is sometimes aimed at the masters of the art, whose performances can seem so detailed that viewers may suspect the scenes are planned.
In order for an improvised scene to be successful, the improvisers involved must work together responsively to define the parameters and action of the scene, in a process of co-creation. With each spoken word or action in the scene, an improviser makes an offer , meaning that he or she defines some element of the reality of the scene. This might include giving another character a name, identifying a relationship, location, or using mime to define the physical environment. These activities are also known as endowment . It is the responsibility of the other improvisers to accept the offers that their fellow performers make; to not do so is known as blocking, negation, or denial, which usually prevents the scene from developing. Some performers may deliberately block (or otherwise break out of character) for comedic effect—this is known as gagging —but this generally prevents the scene from advancing and is frowned upon by many improvisers. Accepting an offer is usually accompanied by adding a new offer, often building on the earlier one; this is a process improvisers refer to as "Yes, And..." and is considered the cornerstone of improvisational technique. Every new piece of information added helps the improvisers to refine their characters and progress the action of the scene. The "Yes, And..." rule, however, applies to a scene's early stage since it is in this stage that a "base (or shared) reality" is established in order to be later redefined by applying the "if (this is true), then (what else can also be true)" practice progressing the scene into comedy, as explained in the 2013 manual by the Upright Citizens Brigade members. 
The unscripted nature of improv also implies no predetermined knowledge about the props that might be useful in a scene. Improv companies may have at their disposal some number of readily accessible props that can be called upon at a moment's notice, but many improvisers eschew props in favor of the infinite possibilities available through mime. In improv, this is more commonly known as 'space object work' or 'space work', not 'mime', and the props and locations created by this technique, as 'space objects' created out of 'space substance,' developed as a technique by Viola Spolin. As with all improv offers , improvisers are encouraged to respect the validity and continuity of the imaginary environment defined by themselves and their fellow performers; this means, for example, taking care not to walk through the table or "miraculously" survive multiple bullet wounds from another improviser's gun.
Because improvisers may be required to play a variety of roles without preparation, they need to be able to construct characters quickly with physicality, gestures, accents, voice changes, or other techniques as demanded by the situation. The improviser may be called upon to play a character of a different age or sex. Character motivations are an important part of successful improv scenes, and improvisers must therefore attempt to act according to the objectives that they believe their character seeks.
Many theatre troupes are devoted to staging improvisational performances and growing the improv community through their training centers.
In addition to for-profit theatre troupes, there are many college-based improv groups in the United States and around the world.
In Europe the special contribution to the theatre of the abstract, the surreal, the irrational and the subconscious have been part of the stage tradition for centuries. From the 1990s onwards a growing number of European Improv groups have been set up specifically to explore the possibilities offered by the use of the abstract in improvised performance, including dance, movement, sound, music, mask work, lighting, and so on. These groups are not especially interested in comedy, either as a technique or as an effect, but rather in expanding the improv genre so as to incorporate techniques and approaches that have long been a legitimate part of European theatre.
Notable contributors to the field
Some key figures in the development of improvisational theatre are Viola Spolin and her son Paul Sills, founder of Chicago's famed Second City troupe and originator of Theater Games, and Del Close, founder of ImprovOlympic (along with Charna Halpern) and creator of a popular longform improv format known as The Harold. Other luminaries include Keith Johnstone, the British teacher and writer–author of Impro , who founded the Theatre Machine and whose teachings form the foundation of the popular shortform Theatresports format, Dick Chudnow, founder of ComedySportz which evolved its family-friendly show format from Johnstone's Theatersports, and Bill Johnson, creator/director of , who pioneered the concept of "Commun-edy Outreach" by tailoring performances to non-traditional audiences, such as the homeless and foster children.
David Shepherd, with Paul Sills, founded The Compass Players in Chicago. Shepherd was intent on developing a true "people's Theatre", and hoped to bring political drama to the stockyards. The Compass went on to play in numerous forms and companies, in a number of cities including NY and Hyannis, after the founding of The Second City. A number of Compass members were also founding members of The Second City. In the 1970s, Shepherd began experimenting with group-created videos. He is the author of "That Movie In Your Head", about these efforts. In the 1970s, David Shepherd and Howard Jerome created the Improvisational Olympics, a format for competition based improv. The Improv Olympics were first demonstrated at Toronto's Homemade Theatre in 1976 and have been continued on as the Canadian Improv Games. In the United States, the Improv Olympics were later produced by Charna Halpern under the name "ImprovOlympic" and now as "IO"; IO operates training centers and theaters in Chicago and Los Angeles. At IO, Halpern combined Shepherd's "Time Dash" game with Del Close's "Harold" game; the revised format for the Harold became the fundamental structure for the development of modern longform improvisation. 
In 1975 Jonathan Fox founded Playback Theatre, a form of improvised community theatre which is often not comedic and replays stories as shared by members of the audience.
The Groundlings is a popular and influential improv theatre and training center in Los Angeles, California. Gary Austin, founder of The Groundlings, continues to teach improvisation around the country, focusing especially in Los Angeles. He is widely acclaimed as one of the greatest acting teachers in America. His work is grounded in the lessons he learned as an improviser at The Committee with Del Close, as well as in his experiences as founding director of The Groudlings. The Groundlings is often seen as the Los Angeles training ground for the "second generation" of improv luminaries and troupes. Stan Wells developed the "Clap-In" style of longform improvisation here, later using this as the basis for his own theatre, The Empty Stage which in turn bred multiple troupes utilizing this style.
In the late 1990s, Matt Besser, Amy Poehler, Ian Roberts, and Matt Walsh founded the Upright Citizens Brigade Theatre in New York and later they founded one in Los Angeles, each with an accompanying improv/sketch comedy school. In September 2011 the UCB opened a third theatre in New York City's East Village, known as UCBeast.
Gunter Lösel compared the existing improvisational theater theories (from Moreno, Spolin, Johnstone, Close...), structured them and wrote a general theory of improvisational theater. 
- Guerrilla theater
- List of improvisational theatre companies
- List of improvisational theater festivals
- Playback Theatre
- Twentieth Century Acting Training . ed. Alison Hodge. New York: Routledge, 2012.
- . interactiveimprov.com .
- Viola Spolin (1999). Improvisation for the Theater Third Edition . ISBN 0-8101-4008-X.
- The story of the Compass Players and its development into The Second City is told by first-hand interviews in Jeffrey Sweet's book "Something Wonderful Right Away" (Limelight Editions, 2004)
- Janet Coleman's "The Compass: The Improvisational Theatre that Revolutionized American Comedy" (Centennial Publications of The University of Chicago Press, 1991).
- Lois Jeary. . exeuntmagazine.com .
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- List of improvisational theatre companies
- Elliot, Chad. . Seattle Improv Classes . Seattle Improv Classes . Retrieved 1 December 2016 .
- Experimental Theatre from Stanislavsky to Peter Brook by James Roose Evans
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- Stephen Colbert 2006 Commencement Address at Knox College
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- Scheiffele, Eberhard (2001). . Research in Drama Education: The Journal of Applied Theatre and Performance . 6 (2): 179–191. doi:.
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- , New York Times , 20 February 2014
- An account of this process which lead up to the development of modern longform improvisation, as seen through first-person accounts of Shepherd and Halpern, can be found in the following documentary film: Mike Fly (2010). .
- Das Spiel mit dem Chaos - Zur Performativität des Improvisationstheaters . Gunter Lösel. Bielefeld: transcript Verlag, 2013.