A beam is a line that connects notes with tails to show rhythmic grouping, which varies according to the metrical structure of the current time signature.

This way of grouping notes helps performers calculate quickly exactly how to play their given rhythm and helps them follow both their part and, if applicable, the conductor.

If appropriate for the current meter and position in the bar, beams are automatically formed in Dorico for iPad when you input two or more adjacent notes or chords that are an eighth note (quaver) or shorter in duration.

Figure 1. Multiple beam groups in a 6/8 time signature

You can find options that control how notes are grouped into beam groups by default in each flow on the Beam Grouping page in Notation Options.