Figure 1. Primary beams.
Figure 2. Secondary beams.
Figure 3. Rules for using beams.
Figure 4. Rules for using beams.
A beam is a horizontal or near-horizontal line that connects the stems or flags of
two or more notes, each less than a quarter note in value, occurring consecutively
within a beat. Beams make such notes easier to read and write. In some cases,
primarily with eighth notes, beams may encompass more than one beat and
up to two beats.
There are two basic types of beams: primary beams and secondary beams. Primary beams link entire note groups together (Figure 1). Secondary beams define further subdivisions of a note-group beamed together by a primary beam (Figure 2).
There are some important rules about beaming. In 4/4 time, a beam should not cross beat 3. Instead, draw two beamed groups. Imagine a line dividing the bar in half (Figure 3).
The grouping of sixteenth notes and triplets must show the start of all four beats. In 6/8, the fourth eighth note must be visible. In 12/8, the seventh eighth note must be visible. Beams on eighth notes, sixteenth notes, or triplets should not cross over the imaginary barline.
Beams also create some exceptions to the rules about stem length and direction. A beam should follow the general direction of the notes, and the shortest stem in the beamed group should be an octave long. The stem direction of the group is determined by the note that is farthest away from the center line. Following these few guidelines makes the difference between unreadable and readable music Figure 4).