Rhythm may be generally defined as a movement marked by the regulating of strong and weak elements or of opposite or different conditions. This general meaning of regular recurrence or pattern in time may be applied to a wide variety of cyclical natural phenomena having a periodicity or frequency of anything from microseconds to millions of years.
Now, for the purpose of this subject, we will not be talking about any periodicity at the extremes of microseconds or millions of years. Music is like an expressive story, with phrases and sentences. You could call each “phrase” a measure. Each measure has the same amount of beats. These are defined by the time signature.
Time signatures were covered extremely briefly in the last chapter. It consists of two numbers, one stacked on the other. The bottom number indicates the note value or length (quarter note, half note, etc.). The top number indicates the number of beats in each measure.
There are various types of meters, including simple, compound, complex, mixed, additive, fractional, irrational, and more. The first three, (simple, compound, and complex) are the most commonly used.
A simple meter is a meter with only two numbers, one on top of the other. A simple meter is a meter in which each beat of the measure divides naturally into two equal parts.
A compound meter is a meter with only two numbers as well. As opposed to a simple meter, each beat in a compound meter can be divided naturally into three equal parts.
A complex meter is usually defined as any meter that does not fall into the categories of simple or compound.
A mixed meter is a meter composed of a meter next to another meter, so that the first meter is in effect for the first measure and the second meter for the second measure. This essentially creates an alternating pattern of rhythm.
The other meters are very uncommon and won’t be covered.