For easy reading, the staff is divided by bar lines into measures.
A MEASURE in music is defined as: The group of beats made by the regular recurrence of primary or heavy accents, the position of which is marked on the staff by bars just before them. Hence the notes or rests between two adjacent bars.
– Bar line
A bar line is used to separate measures. Also used for changes in time signature. Bar lines are extended to connect multiple staves in certain types of music, such as keyboard, harp, and conductor scores, but are omitted for other types of music, such as vocal scores.
– Double bar line Used to separate two sections of music or placed before a change in key signature.
– Bold double bar line Used to indicate the conclusion of a movement or an entire composition.
– Dotted bar line Subdivides long measures of complex meter into shorter segments for ease of reading, usually according to natural rhythmic subdivisions.
– Repeat Bars Repeat Bars enclose a passage that is to be played more than once.