Editing Binary form (section)

==Structure==
A typical example of a piece in binary form has two large sections of roughly equal duration. The first will begin in a certain [[key (music)|key]], which will often, (but not always), [[Modulation (music)|modulate]] to a [[closely related key]]. Pieces in a major key will usually modulate to the [[dominant (music)|dominant]], (the fifth scale degree above the [[tonic (music)|tonic]]). Pieces in a minor key will generally modulate to the [[relative key|relative major key]], (the key of the third scale degree above the minor tonic), or to the dominant minor. A piece in minor may also stay in the original key at the end of the first section, closing with an imperfect [[cadence]].

The second section of the piece begins in the newly established key, where it remains for an indefinite period of time. After some harmonic activity, the piece will eventually modulate back to its original key before ending.

More often than not, especially in 18th-century compositions, the A and B sections are separated by [[bar (music)|double bars]] with repeat signs, meaning both sections were to be repeated.<ref>Bartlette, Christopher, and Steven G. Laitz (2010). ''Graduate Review of Tonal Theory''. New York: Oxford University Press, p. 156. {{ISBN|978-0-19-537698-2}}</ref>

Binary form is usually characterized as having the form ''AB'', though since both sections repeat, a more accurate description would be ''AABB''. Others, however, prefer to use the label ''AA′''. This second designation points to the fact that there is no great change in character between the two sections. The [[rhythm]]s and [[melody|melodic]] material used will generally be closely related in each section, and if the piece is written for a [[musical ensemble]], the [[Instrumentation (music)|instrumentation]] will generally be the same. This is in contrast to the use of [[verse-chorus form]] in [[popular music]]—the contrast between the two sections is primarily one of the keys used.