Painters and photographers design scenes to create a sense of balance, depth and form, drawing the viewer's eye to the subject. Likewise, musicians design musical texture and form as precisely and deliberately as visual artists. Today we look at the basic principles of musical texture and form.
Musical texture refers to how melodic, rhythmic, and harmonic elements combine in music. In other words, the horizontal and vertical aspects of music.
Horizontal
The horizontal or linear aspects of texture revolve around melodic lines. In layman's terms, a melody. When you sing a song, you are singing a melodic line.
Horizontal and Vertical Aspects of Texture | Yellow Bird excerpt
Vertical
The vertical aspect of texture is linked to how melodic lines and chords combine together. For example, singing with a friend while strumming a guitar creates layers of melodic lines and chords. How the two voices and guitar sound together at any given point in time is the vertical aspect of texture.
There are names for textures: monophonic, polyphonic and homophonic. Textural subclasses exist but we'll focus on the three main textures.
Monophonic
Monophonic texture consists of a single melodic line. Sing Row, Row, Row Your Boat by yourself. You just created monophonic texture. It's still monophonic even if your friends join in so long as they sing unison and don't harmonize.
Monophonic | Row, Row, Row Your Boat
Polyphonic
Polyphonic texture is made of two or more lines of relatively equal importance. Sing Row, Row, Row Your Boat but this time your friend joins with "Row, Row" when you get to the word "Gently." Two measures later, your neighbor follows suit. Now there are three independent melodic lines of equal importance, i.e., polyphonic texture. The technique used in Row, Row, Row Your Boat is called imitation: you and your friends are echoing one another.
Polyphonic | Row, Row, Row Your Boat
Homophonic
Finally, sing Row, Row, Row Your Boat but accompany yourself by strumming chords on a guitar while your little sister plays a bass line. This texture, melody with supportive chords, is called homophonic texture.
Homophonic | Row, Row, Row Your Boat
Textures are important characteristics of style and a clue to help describe and distinguish one musical style from another.
To make sense as communication, musical sounds are organized on a timeline. Thus, a key element of music is its temporal quality: musical sounds are connected to one another and unfold through time. As we listen to music, melodies, harmonic progressions, rhythm, etc., stick in our memory. A sense of form is created as prior ideas return and are contrasted with new material. This organization of musical ideas in time is called musical form.
Today we'll examine the universals of musical form. Later, as we work through different musical styles, we'll address details of specific forms.
Musical forms vary throughout history but most are based on the techniques of repetition, variation and contrast.
Repetition
Repetition creates unity, balance and symmetry in a musical work, drawing on our enjoyment of recognizing and remembering something. The easiest thing to recognize is a melody you just heard. Thus, composers repeat melodies to create shape and unity in a composition.
Variation
A key principle of repetition technique is to repeat a musical idea enough to make it memorable. Too many repeats are monotonous. The answer to excess repetition is variation. A variation is a repeat of a prior musical idea—a melody or even fragments of a melody—but with changes to keep it interesting without losing the essential character. Variation has the power of repetition but adds drama due to changes in melody, harmony, rhythm, instruments, key, dynamics, or texture.
Contrast
Contrast is used to create variety, conflict and mood changes. The return of a prior idea is stronger if preceded with a contrasting section. Contrasts may involve a new melody, harmony, instruments, key, tempo, etc.
Simple Songs
Simple songs such as Ode to Joy create form by grouping phrases into patterns. For example, the song structure of chorus and verse is a common musical form.
To determine a song's musical form, we begin by labeling each phrase with a lower case letter: a, b, c, etc.
Identical phrases are labeled with the same letter, e.g., a a.
If phrases are similar but one has a variation, a prime symbol is added: a a'.
A phrase consisting of new material is labeled with a different letter, e.g., a b.
Phrase analysis reveals details of formal structure: phrase repetitions, variations and appearance of new material. The two phrases of Ode to Joy are organized in an a a' relationship, same melodic material but differing cadences:
Ode to Joy | First phrase: a
Ode to Joy | Second phrase: a'
Larger Instrumental Works
Musical form is a template composers pour ideas into. Millions of songs are organized around the chorus-verse form. Although they use the same form, each song sounds different. If every song had a new formal structure, listeners would be confused. We expect music to be organized a certain way.
Like simple songs, larger works employ the principles of repetition, variation and contrast to create form. However, these principles are applied at multiple levels: motive (short melodic idea), phrase and large sections of the work.
Repetition
Listen to how Beethoven introduces and repeats a four-note motive at the beginning of the first movement of Symphony No. 5:
Four-Note Motive | Beethoven's Symphony No. 5, Allegro con brio
Variation
Beethoven imprints the motive into memory by repeating and varying it incessantly.
Contrast
Near the end of the track, Beethoven introduces a contrasting melody, a more lyrical and gentler theme:
Symphony No. 5: 1. Allegro con brio | Beethoven excerpt (1:04) )
Ternary Form
In form analysis we use capital letters (A) to symbolize major sections of a piece and the prime symbol to indicate variation of repeated sections (lower case is used for phrases). For example, A B A means there are three sections: two identical outer sections (A) and a contrasting middle section (B).
Use of two identical or similar outer sections to frame a contrasting middle section is a near universal formal structure. It's called ternary form (three-part form). Ternary form has been varied endlessly throughout history: minuet and trio, sonata form, da capo aria, and a long list of popular and jazz variations.
Ternary form has common variants: A A B A' means the A section is repeated, followed by a contrasting middle section (B) and, finally, the first section returns with variations (A'). The term, coda, means a ending section has been added.
Pipeline is a textbook example of ternary form:
| A | A | B | A |
The A section is heard twice in the first section of the piece. The B section, 1:09, introduces a new theme and builds tension with forte dynamics. After the solos by Kealoha, Deither and Colsen, the A section returns at 3:03.
Pipeline | Leeward Coast Guitars (4:15)
There are many other musical forms and we'll address them as we work through the stylistic eras in this textbook.
Musical Texture
Horizontal
Vertical
Monophonic
Polyphonic 
Homophonic
Musical Form
Repetition
Variation 
Contrast
Ternary Form 
