Almost all music that exists is created from two elements:

1. Pitch
2. Rhythm

Pitch is defined in the following way:

the quality of a sound governed by the rate of vibrations producing it; the degree of highness or lowness of a tone. (Google)

Pitch is a perceptual property of sounds that allows their ordering on a frequency-related scale,^[1] or more commonly, pitch is the quality that makes it possible to judge sounds as "higher" and "lower" (Wikipedia)

Rhythm is defined in the following way:

a strong, regular, repeated pattern of movement or sound. (google)

the systematic arrangement of musical sounds, principally according to duration and periodic stress (google)

The study of music theory is the study of these two elements of music and how they work together. The more subtle aspects of these definitions will clarify as we continue. To start, let's look at rhythm.