Contrary motion
Encyclopedia
In music theory
Music theory
Music theory is the study of how music works. It examines the language and notation of music. It seeks to identify patterns and structures in composers' techniques across or within genres, styles, or historical periods...

, contrapuntal motion is the general movement of two melodic lines
Melody
A melody , also tune, voice, or line, is a linear succession of musical tones which is perceived as a single entity...

 with respect to each other. In traditional four-part harmony
Four-part harmony
The term "four-part harmony" refers to music written for 4 voices, or 4 musical instruments, where the various parts give a different note of each chord of the music. Typically, the 1st of the 4 parts will sing the melody, with the other 3 parts providing the supporting harmonies...

, it is important that lines maintain their independence, an effect which can be achieved by the judicious use of the four types of contrapuntal motion: contrary motion, similar motion, parallel motion, and oblique motion.

Contrary motion is motion in opposite directions. That is, when one of the lines moves up, the other line moves down. If the voices always move by the same intervals (in opposite directions) they are said to be in strict contrary motion.

The following example shows two voices in contrary motion:

Contrary motion is important to maintain independence of melodic movement in contrapuntal writing.

Similar motion is motion in the same direction, but with the interval between them changing. In other words, both lines move up, or both lines move down, but the interval between them is different in the first chord and the second chord. For example:


Oblique motion is motion of one melodic line while the other remains at the same pitch. For example:

Similar and oblique motion provide less independence than contrary motion, but more than parallel motion.

Parallel motion is motion in the same direction, keeping the same interval between them. For example:

Parallel motion at an interval of a perfect fifth
Perfect fifth
In classical music from Western culture, a fifth is a musical interval encompassing five staff positions , and the perfect fifth is a fifth spanning seven semitones, or in meantone, four diatonic semitones and three chromatic semitones...

 is known as parallel or consecutive fifths
Consecutive fifths
In music, consecutive fifths are progressions in which a perfect fifth is followed by a different perfect fifth between the same two musical parts : for example, from C to D in one part along with G to A in a higher part...

, and at an interval of an octave
Octave
In music, an octave is the interval between one musical pitch and another with half or double its frequency. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems"...

 is known as parallel or consecutive octaves. These motions are generally avoided in traditional counterpoint
Counterpoint
In music, counterpoint is the relationship between two or more voices that are independent in contour and rhythm and are harmonically interdependent . It has been most commonly identified in classical music, developing strongly during the Renaissance and in much of the common practice period,...

because they offer the lines so little independence from each other.
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