Anacrusis
In poetic and musical meter, and by analogy in publishing, an anacrusis (from , , literally: 'pushing up', plural "anacruses") is a brief introduction (not to be confused with a literary or musical introduction, foreword, or with a preface). It is a set of syllables or notes, or a single syllable or note, which precedes what is considered the first foot of a poetic line (or the first syllable of the first foot) in poetry and the first beat (or the first beat of the first measure) in music that is not its own phrase, section, or line and is not  considered part of the line, phrase, or section which came before, if any. Poetry. In poetry, a set of extrametrical syllables at the beginning of a verse is said to stand in anacrusis ( "pushing up"). "An extrametrical prelude to the verse," or, "extrametrical unstressed syllables preceding the initial lift." The technique is seen in Old English poetry, and in lines of iambic pentameter, the technique applies a variation on the typical pentameter line causing it to appear at first glance as trochaic. Below, the anacrusis in the fourth line of William Blake's poem "The Tyger" (with punctuation modernized) is  in italics: The poem is in trochaic tetrameter, in which the first syllable of each line is expected to be stressed, but the fourth line begins with the additional unstressed syllable "Could". Music. In music, an anacrusis (also known as a pickup, or fractional pick-up) is a note or sequence of notes, a motif, which precedes the first downbeat in a bar in a musical phrase. "The span from the beginning of a group to the strongest beat in the group." Anacrusis, especially reoccurring anacrusis (anacrusis motif played before every measure or every other measure), "is a common means  of weighting the first beat," and thus strengthening or articulating the meter. The musical term is inferred from the terminology of poetry. Anacruses may involve fine details such as rhythm and phrasing, or may involve wider features such as musical form (such as when used repeatedly). The anacrusis is a perceived grouping which is context generated in the individual phrasing of a concrete composition. The grouping of one or more antecedent tone events to a perceived phrase gestalt may be rhythmically evoked by their temporal proximity to the phrase's first downbeat (perceived phrase onset). An anacrusis may also be  evoked solely metrically (non-rhythmically), i.e. tonally, that is, without the downbeat perception enforced by a relative long value. Although the anacrusis is integrated in a musical phrase gestalt (grouped to it), it is not located in the perceived 'body' of the phrase (which is spanning from its first downbeat to its ending beat), but before the phrase (hence the German term "Auftakt"; literally: "upbeat"). In this respect – in a sequence of phrases – the anacrusis also may be perceived 'between' two phrases, neither being perceived as part of the ending of a former one, nor being located in the following  one. Outside of that the term of the anacrusis is most commonly used where it applies everywhere else 'within' the 'body' of the phrase between the 'head' (first downbeat) and the 'foot' (ending beat) where, by what ever musical means, a grouping is perceived from an upbeat to a downbeat (especially also to the phrases ending beat). Since an anacrusis "is an incomplete measure that allows the composition[, section, or phrase] to start on a beat other than one," if anacrusis is present, the first bar after the anacrusis is assigned bar number 1, and Western standards for musical notation  often include the recommendation that when a piece of music begins with an anacrusis, the notation should omit a corresponding number of beats from the final bar of the piece, or the final bar before a repeat sign, in order to keep the length of the entire piece at a whole number of bars. This final partial measure is the complement. However, an anacrusis may last an entire bar. Other fields. In academic publishing, the term is sometimes used in an article to mark an introductory idea standing between the abstract and the introduction proper.