In musical notation, a beam is a horizontal or diagonal line used to connect multiple consecutive notes (and occasionally rests) in order to indicate rhythmic grouping. Only eighth notes (quavers) or shorter can be beamed. The number of beams is equal to the number of flags that would be present on an un-beamed note.
The span of beams indicates the rhythmic grouping, usually determined by the time signature. Therefore, beams do not usually cross bar lines, or major sub-divisions of bars. If notes extend across these divisions, this is indicated with a tie.
In modern practice beams may span across rests in order to make rhythmic groups clearer.
In vocal music, beams were traditionally used only to connect notes sung to the same syllable. In modern practice it is more common to use standard beaming rules, while indicating multi-note syllables with slurs.
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 beams usually go above the note head, otherwise they go below.
Feathered beaming shows a gradual change in the speed of notes. It is shown with a primary straight beam and other diagonal secondary beams (that together resemble a feather, hence the name). These secondary beams suggest a gradual acceleration or deceleration from the first note value within the feathered beam to the last. The shortest value possible to show being the eighth note (quaver). When the number of notes played is not of interest, but rather the effect of acceleration or deceleration, an approximate number of headless stems are used. To ensure clarity, sometimes the number of notes within the beam, or the duration of the total beamed notes, is shown above the music, as is done with tuplets.
- Standard Music Notation Practice Music Publishers' Association of the United States (Accessed: 4 April 2013)
-  (Accessed 26 March 2015)