Notes are given a specific value of time in order to establish how long to hold those particular notes. These values, along with the time signature (discussed in the next section) direct a musician on how to play the notes in a piece. After determining what note must be played, a musician must know how much value that particular note holds – this is determined by the composition of the note itself. (All of the below examples are illustrated in 4/4 time for the sake of simplification).
A whole note or semibreve is an open circle that has a value of 4 beats. A half note or minim is an open circle with a stem, attached to the right or left side (the stem may point up or down and is usually uniform throughout the bar or measure) and is given a value of 2 beats. A quarter note or crotchet is a blackened circle with a stem attached to either the right or left side of the note (just as with the half note) and is given a value of 1 beat. The eighth note or quaver is a blackened circle with a stem and tail attached, and is given the value of ½ a beat.
The sixteenth note or semiquaver is a blackened circle with a stem and two tails, and is given a value of ¼ a beat. From the sixteenth note, the thirty second note is written as a blackened circle with a stem and three tails. The sixty-fourth note is written as blackened circle with a stem and four flags. These note values continue being divided by two. It is rare to see annotations above the thirty-second note because of the minuscule time for which they’re held (excepting some guitar solos).
Stems, tails and beams annotate note values. These annotations are to aid the musician in readily identifying the amount of time for which to hold the note. When a group of stemmed notes appear in a measure, a beam groups them. Just as notes must be held for a requisite amount of time, so must the time for which nothing is played – these are appropriately called rests. These rests complete the value of the measure itself to keep with the time signature. Notes and rests can also be given more value by way of dots – called dotted notes and rests; these add one half of a beat.