Notes are not just displayed on the 5 lines and 4 spaces of each clef. As illustrated on the right, the use of ledger lines above and below each staff or grand staff is also used. In the example to the right, 8va means that notes are played an octave higher and 8vb means that notes are played one octave lower. The use of ledger lines to represent notes above staffs occurs frequently and can be determined by how many lines are shown above or below the staff. Middle C is generally written on a ledger line and can be shown above the bass clef, below the treble clef or between them on a grand staff. Not all instruments make use of the grand staff. Some use just the bass or treble clef. Choirs generally make use of a C clef.

In the fifteenth century bar lines were introduced, dividing written music into bars or measures. These are two terms commonly used to define rhythm within music. Many people who can't read music will refer to the number of "beats" in a measure -- and this itself, is determined by the time signature used in piece of music. 4/4 is commonly used and has strong beats and weak beats, as illustrated at Brian Blood's website.