Dividing the music into bars helps you to keep time by counting beats for your head or under your breath. Bar lines vertical lines mark the start and the top of the bar. Time signatures have a top and a bottom part: the end determines the number of beats and the bottom determines the kind of beat. The time signature is written once after the clef initially of a piece of music unless it adjustments. The way the beats are grouped also is dependent upon the time signature, but this will become more obvious as you increase event of reading music. The tempo tells you the way simply the music might be played. Usually, tempo is expressed in beats per minute bpm for a particular beat type. This means 50 crochet beats in a minute. To can help you play at the correct tempo, that you may use a metronome. These can be either analogue or electronic but the feature is the same: it ticks or bleeps on each beat at the set tempo. Metronomes can be especially helpful for orchestras or bands to keep everybody in time with one another.