A beam in musical notation is a thick line frequently used to connect multiple consecutive eighth notes (quavers), or notes of shorter value (indicated by two or more beams), and occasionally rests. Beamed notes or rests are groups of notes and rests connected by a beam; the use of beams is called beaming.
Span and grouping
The span of beams indicates the rhythmic grouping, usually determined by the time signature. In modern practice beams may span across rests in order to make rhythmic groups clearer. Notes lasting a quarter note (crotchet) or longer cannot be beamed.
In vocal music, beams are traditionally used only to connect notes sung to the same syllable. Since this often breaks the rhythmic grouping the rhythms are more difficult to read. In modern engraving practice it is commonplace to beam notes regardless of the words, and to add slurs to emphasize where multiple notes are sung to the same syllable.
Notes joined by a beam usually have all the stems pointing in the same direction (up or down). The average pitch of the notes is used to determine the direction - if the average pitch is below the middle staff-line, the stems and beam(s) usually go above, otherwise they usually go below.
In music engraving there are various more complex rules governing the positioning and angle of beams.
- Standard Music Notation Practice Music Publishers' Association of the United States (Accessed: 4 April 2013)