The lines in the beat in vocal music refer to the bar lines.
Two sections are separated by a "section line". The bar line is a thin line perpendicular to the staff, with five lines on top and one line on the bottom, which just cuts off the staff. No matter how far away the upper and lower lines are from the staff, the bar line cannot go beyond the staff. Draw two bar lines in the last section of the work, and the one on the right is thicker, indicating the end of a work or a paragraph.
The beat after the bar line must be a strong beat, and there is only one strong beat in each bar, and the rest are weak beats.
Music always alternates between strong beats and weak beats. This alternation cannot be chaotic or arbitrarily arranged. Instead, it should form a minimum beat to organize a small section according to certain rules, and then repeat the cycle based on this. . For example, when there is only one weak beat between two strong beats, it is called "two beats", and 2/4 beat is this type; when there are two weak beats between two strong beats, it is called "triple beat", Like 3/4 and 3/8; there are three weak beats between the two strong beats, which are called "four beats", and the most common one is 4/4.