Harmony is the vertical component of music. It is responsible for the chords created in harmony. The major difference between classical and popular music is the use of harmony. Classical music will use complex chord progressions to create sophisticated music while popular music concentrates on common chord progressions. A typical classical piece might have seven or eight different chords per phrase. In contrast, a popular piece might only have two or three chords. Most musicians will study harmony to analyze and gain a greater understanding of the music.
Melody is the horizontal component of music that we typically refer to as a tune. The melody is the most recognizable part of any composition. In classical music, melodies are complex and borrow pitches from keys that are closely related. In this sense, a composition written in D major will borrow notes from other keys. Borrowing helps to add variety and an element of surprise to the composition. Melody can be broken down into smaller components called motives. Motives are small musical ideas that help to build melodies. A common motive is the 4-note figure from Beethoven's Fifth Symphony.
Timbre is an essential component for composers and orchestrators. It described the tone color of each individual instrument. Each instrument has its own characteristic sound and produces a timbre that adds color and variety to a composition. Composers will make use of several different-sounding instruments to create new combinations of sounds. Timbre occurs most notably in orchestral scores that combine brass, woodwind, string, percussion and keyboard instruments to create the overall symphonic texture.
Form is the most crucial component of classical music. Without form, music would lose its direction and become an amorphous and undefined mass of sound. Form helps to create compositions in which melodies repeat themselves in logical ways. Even compositions that are through-composed, in which no section repeats, will include repetitive motifs to help add structure to the composition. Letters indicate specific repeated sections. For instance, a composition that labeled ABA will have two repeated sections at the beginning and end of the piece and a new, related section in the middle.