Music has not always be written the same way. As stated at Gabriella Scelta's Music Symbol site, by the 1700s, the use of a five line staff to write music was firmly established. According to Exploring The Arts Foundation, the use of a 4 line staff appeared in the 10th century and a system of fixed note lengths arose in the 14th century. "Vertical bar lines that divide the staff into sections appeared in the 15th century. By the early 16th century, notation had assumed much of its modern form, with the essential components of staff, clef, Time signature and durational values, though bar lines only gradually became widespread during the 16th and 17th centuries as an aid in ensemble performance. Regular measures (bars) became commonplace by the end of the 17th century." Music today is still evolving and practices used in Western Music have been adopted by all musicians worldwide. Modern music evolved from plainsong notation.

Music is written on a five line staff. It's predecessor, a 4 line staff (Neumes), is mistakenly attributed to Guido of Arezzo, but he did not invent any staffs. He invented a notation system to assist Gregorian singers. A comparison of the two staff systems illustrates how musical notes can be written down. What made Guido of Arezzo famous is his Guidonian Hand (Manis Guidonis), that is illustrated below the modern 5 line staff. It helped Gregorian singers to sight read written music and introduced the first use of solfege. staff

guido
The clefs commonly in use today are the Treble Clef (G Clef) and the Bass Clef (F Clef). These clefs encircle around G and F as shown on the right. The mnemonics used to memorize the notes of these clefs is illustrated in the top diagram. At this point in time, we will dispense with the pitch references G4 and F3 respectively as most people do not refer to their respective octaves by saying that they are going to play "G4" or "F3" ... or "C4" (Middle C). Those who memorize the clef notes, should just use the letter associated with the note.

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. octiva, ledger lines
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.

bar lines, measures