It is the way the composer arranges notes in time. Some notes may last a short time, and others a relatively long time. Rhythm helps give music its character. Another important element of rhythm is accent. Most composers build their music on a pattern of regularly occurring accents. For example, a waltz follows a strong-weak-weak pattern, ONE two three ONE two three. A march has a strong-weak pattern, ONE two ONE two. To create a rhythm pattern you need different music symbols, such as quarters, half, or whole notes and rests.
The composer combines pitches and rhythms to create a melody, or tune. Some short pieces of music have only one melody. Longer pieces may consist of different melodies to give the music contrast and variety. To create a melody you different pitches.