Music Theory: "My Fickle Friend"

Consonance and dissonance

Main article: Consonance and Dissonance
Consonance can be roughly defined as harmonies whose tones complement and increase each others' resonance, and dissonance as those which create more complex acoustical interactions (called 'beats'). A simplistic example is that of "pleasant" sounds versus "unpleasant" ones. Another manner of thinking about the relationship regards stability; dissonant harmonies are sometimes considered to be unstable and to "want to move" or "resolve" toward consonance. However, this is not to say that dissonance is undesirable. A composition made entirely of consonant harmonies may be pleasing to the ear and yet boring because there are no instabilities to be resolved.

Melody is often organized so as to interact with changing harmonies (sometimes called a chord progression) that accompany it, setting up consonance and dissonance. The art of melody writing depends heavily upon the choices of tones for their nonharmonic or harmonic character.
"Harmony" as used by music theorists can refer to any kind of simultaneity without a value judgement, in contrast with a more common usage of "in harmony" or "harmonious", which in technical language might be described as consonance.

Dynamics
Main article: Dynamics (music)
In music, dynamics normally refers to the softness or loudness of a sound or note, e.g. pianissimo or fortissimo. Until recently, most of these dynamics and signs were written in Italian, but recently are becoming written or translated into English. However, to every aspect of the execution of a given piece, either stylistic (staccato, legato etc.) or functional (velocity) are also known as dynamics. The term is also applied to the written or printed musical notation used to indicate dynamics.

Texture
Main article: Musical texture
Musical texture is the overall sound of a piece of music commonly described according to the number of and relationship between parts or lines of music: monophony, heterophony, polyphony, homophony, or monody. The perceived texture of a piece may also be affected by the timbre of the instruments, the number of instruments used, and the interval between each musical line, among other things.
Monophony is the texture of a melody heard only by itself. If a melody is accompanied by chords, the texture is homophony. In homophony, the melody is usually but not always voiced in the highest notes. A third texture, called polyphony, consists of several simultaneous melodies of equal importance.

Form or structure
Main article: Musical form
Form is a facet of music theory that explores the concept of musical syntax, on a local and global level. The syntax is often explained in terms of phrases and periods (for the local level) or sections or genre (for the global scale). Examples of common forms of Western music include the fugue, the invention, sonata-allegro, canon, strophic, theme and variations, and rondo. Popular Music often makes use of strophic form often in conjunction with Twelve bar blues.

Theories of harmonization