This is an introduction to different types of composition.
Types of Composition
A chord progression is a series of chords, notes that are played simultaneously, played in order. The amount of time on each chord in a progression may vary, and this is called the harmonic rhythm. Melodic lines are typically added by writing the melody using primarliy notes from the chord, though other, generally short, "passing" and "approach" notes should be used to add variety.
Traditional part writing is often based on counterpoint, in which a second melody is written to use harmonic intervals that create primarily consonant relationships between notes. First, a leading melodic line must be written, then contrapuntal methods may be used to add additional melodic lines. Consonants are further divided into perfect and imperfect consonances and contrasted to dissonances. Traditionally the unison, the octave and the fifth were considered perfect consonances while the third and sixth were considered imperfect consonances; the fourth was considered a dissonance if it was above the leading line but a consonance if below, though modern theorists have questioned the need for this distinction. Other intervals are considered dissonant. Additional melodic lines beyond the second may be added by writing them in counterpoint to all the lines already written.
In addition, the types of movement made a difference. In early theory there were three types of movement: direct, in which both melodic line move in the same direction, oblique in which one line moves and the other does not, and contrary in which both lines move in opposite directions. Some modern theorist further divide direct motion into similar motion, in which both lines move different distances in the same direction, and parallel motion in which both line maintain the same interval between them. Early counterpoint texts (such as Johann Joseph Fux's Gradus ad Parnasum) listed several rules for moving lines, however these can be boiled down to one: Don't move from perfect consonance to perfect consonance by direct motion. The addition of dissonance may be added on an off beat, to be resolve to on the next on beat. Large jumps are discouraged, and it is recommended that they be followed by stepwise motion in the opposite direction. The octave should be used vary sparingly and the unison avoided, however, as these tend to make the melodic lines blur together.
Various rhythms could be used in the various melodic line, and this was encouraged with the goal being "florid counterpoint" in which various rhythms mix in an elaborate way. If a smaller note is used in the following line then dissonance must be on the second note; if the following note starts after the leader, then it must start on the dissonance. Of course, neither have to be dissonant, and a consonance may be used in both places. A series of stepwise movements may also be used to move over several dissonance between consonances. However, two notes one semitone apart (sometimes described as "fa on mi") should always be avoided.
Note that a modern composition that follows a chord progression may just write all parts to fit the same chord, however, use of contrapuntal principles may still be useful in order to make to melodic lines work better together.
Twelve-tone Composition is a composing method that uses all tones of the chromatic scale in any order and at any octave, this is called an ordered tone row. The only rule to this is that every tone has to be played once before another may be repeated. An easy (though never actually used) row is the chromatic scale itself.
The row may present itself in several ways, as a transposition, an inversion, a retrograde, or any combination of these transformations.
Complement and Contrast
A composition is made up of a series of musical phrases which can either complement or contrast each other. A complementary phrase is one which sounds similar to previous phrases, and can be made by, for example, transposing the previous phrase, using the same set of chords, using the same rhythmic pattern, or slightly varying certain notes, among other things. A contrasting phrase, on the other hand, is one that sounds entirely different from previous phrases and often serves as a fill or transition between different parts of a piece.
Good compositions will usually have a balance of complementary and contrasting phrases: a piece which is too complementary will be repetitive and boring, whereas a piece with too much contrast will seem to lack organization and will be difficult to follow.