A beat is a pulse of sound that is louder than other sounds in the music. Beats -- which usually exist in groups and form a pattern -- are characteristic to drums and other low-frequency instruments. Beats add more rhythm to the song by creating a low-frequency foundation and contrasting with high-frequency sounds.
A measure is a group of beats that follows a repetitive pattern. One of the most common measures is the four-beat measure, which indicates that beats are grouped in repetitive four-beat groups. The measure is especially useful for performers and disc jockeys, as it allows them to predict when the song's rhythm will change.
The tempo -- which indicates the song's speed -- measures the number of beats played in a minute, or BPM. A higher tempo will result in more beats and a faster track, while a lower tempo will result in a slower track. Musical genres are easily distinguishable by their tempo, as each genre has a corresponding tempo range.
Melody represents the succession of sounds played within a song. The melody can comprise one or more instruments, playing all at once or alternatively. For a song to sound good, the melody must follow the measure and tempo of the song and be synchronized with the beats.