Ad libitum
Encyclopedia
Ad libitum is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for "at one's pleasure"; it is often shortened to "ad lib" (as an adjective
Adjective
In grammar, an adjective is a 'describing' word; the main syntactic role of which is to qualify a noun or noun phrase, giving more information about the object signified....

 or adverb
Adverb
An adverb is a part of speech that modifies verbs or any part of speech other than a noun . Adverbs can modify verbs, adjectives , clauses, sentences, and other adverbs....

) or "ad-lib" (as a verb
Verb
A verb, from the Latin verbum meaning word, is a word that in syntax conveys an action , or a state of being . In the usual description of English, the basic form, with or without the particle to, is the infinitive...

 or noun
Noun
In linguistics, a noun is a member of a large, open lexical category whose members can occur as the main word in the subject of a clause, the object of a verb, or the object of a preposition .Lexical categories are defined in terms of how their members combine with other kinds of...

). The roughly synonymous phrase a bene placito ("at [one's] good pleasure") is less common but, in its Italian form a piacere, entered the musical lingua franca
Lingua franca
A lingua franca is a language systematically used to make communication possible between people not sharing a mother tongue, in particular when it is a third language, distinct from both mother tongues.-Characteristics:"Lingua franca" is a functionally defined term, independent of the linguistic...

(see below).

Music or rhythm

As a direction in sheet music
Sheet music
Sheet music is a hand-written or printed form of music notation that uses modern musical symbols; like its analogs—books, pamphlets, etc.—the medium of sheet music typically is paper , although the access to musical notation in recent years includes also presentation on computer screens...

, ad libitum indicates that the performer or conductor has one of a variety of types of discretion with respect to a given passage:
  • to play the passage in free time
    Free time (music)
    Free time is a type of musical meter free from musical time and time signature. It is used when a piece of music has no discernible beat. Instead, the rhythm is intuitive and free-flowing. There are five ways in which a piece is indicated to be in free time:...

     rather than in strict or "metronomic
    Metronome
    A metronome is any device that produces regular, metrical ticks — settable in beats per minute. These ticks represent a fixed, regular aural pulse; some metronomes also include synchronized visual motion...

    " tempo
    Tempo
    In musical terminology, tempo is the speed or pace of a given piece. Tempo is a crucial element of any musical composition, as it can affect the mood and difficulty of a piece.-Measuring tempo:...

     (a practice known as rubato when not expressly indicated by the composer);
  • to improvise a melodic line fitting the general structure prescribed by the passage's written notes or chords;
  • to omit an instrument part, such as a nonessential accompaniment
    Accompaniment
    In music, accompaniment is the art of playing along with an instrumental or vocal soloist or ensemble, often known as the lead, in a supporting manner...

    , for the duration of the passage; or
  • in the phrase "repeat ad libitum," to play the passage an arbitrary number of times (cf. vamp).


Note that the direction a piacere (see above) has a more restricted meaning, generally referring to only the first two types of discretion. Baroque music
Baroque music
Baroque music describes a style of Western Classical music approximately extending from 1600 to 1760. This era follows the Renaissance and was followed in turn by the Classical era...

, especially, has a written or implied ad libitum, with most composers intimating the freedom the performer and conductor have.

For post-Baroque classical music and jazz, see cadenza
Cadenza
In music, a cadenza is, generically, an improvised or written-out ornamental passage played or sung by a soloist or soloists, usually in a "free" rhythmic style, and often allowing for virtuosic display....

.

Biology

Ad libitum is also used in psychology
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

 and biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

 to refer to the "free-feeding" weight of an animal, as opposed, for example, to the weight after a restricted diet or pair feeding. For example, "The rat's ad libitum weight was about 320 grams." In nutritional studies, this phrase denotes providing an animal free access to feed or water thereby allowing the animal to self-regulate intake according to its biological needs. For example, "Rats were given ad libitum access to food and water."

In biological field studies it can also mean that information or data were obtained spontaneously without a specific method.

Medical prescription
Medical prescription
A prescription is a health-care program implemented by a physician or other medical practitioner in the form of instructions that govern the plan of care for an individual patient. Prescriptions may include orders to be performed by a patient, caretaker, nurse, pharmacist or other therapist....

s may use the abbreviation ad lib. to indicate "freely" or that as much as one desires should be used.

Drama

Ad-lib is used to describe individual moments during live theatre when an actor speaks through their character using words not found in the play's text. When the entire performance is predicated on spontaneous creation, the process is called improvisational theatre
Improvisational theatre
Improvisational theatre takes many forms. It is best known as improv or impro, which is often comedic, and sometimes poignant or dramatic. In this popular, often topical art form improvisational actors/improvisers use improvisational acting techniques to perform spontaneously...

.

In film
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

 the term ad-lib usually refers to the interpolation of unscripted material in an otherwise scripted performance. In interviews, Dustin Hoffman
Dustin Hoffman
Dustin Lee Hoffman is an American actor with a career in film, television, and theatre since 1960. He has been known for his versatile portrayals of antiheroes and vulnerable characters....

 says he ad-libbed the now famous line, "I'm walking here! I'm walking here!" as "Ratso" Rizzo in Midnight Cowboy
Midnight Cowboy
Midnight Cowboy is a 1969 American drama film based on the 1965 novel of the same name by James Leo Herlihy. It was written by Waldo Salt, directed by John Schlesinger, and stars Dustin Hoffman and newcomer Jon Voight in the title role. Notable smaller roles are filled by Sylvia Miles, John...

.

Live performers such as television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

 talk-show hosts (e.g., Conan O'Brien
Conan O'Brien
Conan Christopher O'Brien is an American television host, comedian, writer, producer and performer. Since November 2010 he has hosted Conan, a late-night talk show that airs on the American cable television station TBS....

, David Letterman
David Letterman
David Michael Letterman is an American television host and comedian. He hosts the late night television talk show, Late Show with David Letterman, broadcast on CBS. Letterman has been a fixture on late night television since the 1982 debut of Late Night with David Letterman on NBC...

, etc.) sometimes enhance their reputation for wit by the delivery of material that sounds ad-libbed but is actually scripted, and may employ ad-lib writers to prepare such material. Some actors are also known for their ability or tendency to ad-lib, such as Peter Falk
Peter Falk
Peter Michael Falk was an American actor, best known for his role as Lieutenant Columbo in the television series Columbo...

 (of the series Columbo), who would ad-lib such mannerisms as absent-mindedness while in character.
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