As mentioned, the notes are given specific values in which they are to be held in order for the melody to be recited. These notes are grouped together in a measure on the staff, divided by bars. A bar divides each measure and these divisions are given a sum value based on the time signature of that measure.
The most common time signature is its own namesake – common time or C. This time signature is known as 4/4 time or common time meaning that the measure contains four notes and each is note value is a quarter note. The first number of the time signature defines how many beats are in the measure and the second number defines the value of those notes. Most contemporary pop, rock, blues, country, and R&B songs are in 4/4 time.
Another common time signature in music is 3/4 time. This means that there are three notes in each measure and each note is a quarter note value. (A complete measure would contain the equivalent of three quarter notes). Cut time or 2/4 time is also common is music. This means that there are only two notes in each measure and that each note is given a quarter note value. (A complete measure would contain the equivalent of two quarter notes).
Of course, there are other time signatures found throughout musicincluding classical, as well as other intricate genres, such as jazz, reggae, and even rock. These remaining time signatures are usually awkward, and do not “divide up” as evenly – consequently, they are not as “danceable”.
Such time signatures are 7/8 time, 5/4 time, and 9/8 time. For instance, the song Money by Pink Floyd is in 7/8 time. To find the time signature of a song, simply tap your foot or snap your finger to the beat and count how many taps are in the reoccurring “phrase”. For instance, listen to the song in the above example, Money and tap your foot or snap to the reoccurring “phrase” in that song. When you tap or snap out the song, begin to sing the numbers with the beat like such: 1, 2, 3, 4, 5, 6, 7; 1, 2, 3, 4, 5, 6, 7. Once you’ve established this count, you can see that there are 7 beats in each measure. Finding the value of those beats is a bit more difficult, and will come over time. However, in this example, common sense lends a great deal to decipher the value. It would sound awkward to assign each of these 7 beats a value for less than the sum total. So, quarter note values are not practical, but eight note values are. Also, another consideration is that the first or top number of the time signature is usually smaller than the second or bottom number.
Next, these notes, in these time signatures, must be grouped in order to form a more readable and comprehensive piece. This is called beaming and is done simply by drawing a “bar” across notes with values less than a quarter beat. Consequently, eighth notes, sixteenth notes, et cetera, are all beamed to allow the musician to read the piece without going insane. Imagine a measure with eight notes, with two tails on each, and four notes with one tail. This would be enough to drive anyone to the brink of insanity. Of course, with the beaming of these notes, come some rules. These rules are designed to allow easier reading and help to define the division of the beat itself.
The first is that notes, in any time signature, should not be beamed across a bar line. All eighth, sixteenth, thirty-second, et cetera should be beamed together to total one beat. Eighth notes ought to be beamed across beats, as before mentioned, except across the second and third beats.
In any time signature, the notes must contain the sum amount of value for that particular time signature. In other words, a 4/4 signature must contain the equivalent of four-quarter notes. A 3/4 signature must contain the equivalent of three-quarter notes and a 7/8 signature must contain the equivalent of seven eighth notes. As for writing notes, so writing rests also have rules. If any of the time signatures (e.g. 4/4, 3/4, 7/8) have a rest in the measure, they must either complete or total the sum value of that particular signature.
For instance, in a 4/4 signature, if there are three quarter notes, there must be a quarter note rest to complete that measure.
Conversely, a measure can be indicated by just a rest, absent any notes. A whole rest can stand for any measure in any time signature because a whole rest is understood to stand for the sum total of the value of the measurelike in the above examples.
With this in mind, one must remember the introduction, that anything is possible in music theory. Therefore, the rule above is not absolute. There is a phenomenon in writing a measure that does not equal the sum total of the assigned time signature, this is called an anacrusis. This is a measure that contains only one beat in the first measure. When this occurs, the last measure is usually incomplete as well. The anacrusis is also known as a lead-in.
These types of happenings do not occur regularly in modern music and do not give license to place an anacrusis in the middle of a composition. Keep in mind that although there are oddities in music theory, they are much like English grammar (there are exceptions to many of the rules).