Metric levels: beat level shown in middle with division levels above and multiple levels below.
In music and music theory, the beat is the basic unit of time, the pulse (regularly repeating event), of the mensural level (or beat level). The beat is often defined as the rhythm listeners would tap their toes to when listening to a piece of music, or the numbers a musician counts while performing, though in practice this may be technically incorrect (often the first multiple level). In popular use, beat can refer to a variety of related concepts including: pulse, tempo, meter, specific rhythms, and groove.
Metric levels faster than the beat level are division levels, and slower levels are multiple levels. Beat has always been an important part of music. Some music genres such as disco will in general de-emphasize the beat, while other such as funk emphasize the beat to accompany dance.
As beats are combined to form measures, each beat is divided into parts. The nature of this combination and division is what determines meter. Music where two beats are combined is in duple meter, music where three beats are combined is in triple meter. Music where the beat is split in two are in simple meter, music where the beat is split in three are called compound meter. Thus, simple duple (2/4, 4/4, 2/2, etc.), simple triple (3/4), compound duple (6/8), and compound triple (9/8). Divisions which require numbers, tuplets (for example, dividing a quarter note into five equal parts), are irregular divisions and subdivisions. Subdivision begins two levels below the beat level: starting with a quarter note or a dotted quarter note, subdivision begins when the note is divided into sixteenth notes.