Often a musical form becomes so popular with composers that it is given a name. For example, if a piece of music is called a "theme and variations", it is expected to have an overall plan quite different from a piece called a "rondo". (Specifically, the theme and variations would follow an A A' A" A"'... plan, with each section being a new variation on the theme in the first section. A rondo follows an A B A C A ... plan, with a familiar section returning in between sections of new music.)
Also, many genres of music tend to follow a preset form, like the "typical pop song form" in Figure 5.39. A symphony, for example, is usually a piece of music written for a fairly large number of instruments. It is also associated with a particular form, so knowing that a piece of music is called a symphony should lead you to expect certain things about it. For example, listeners familiar with the symphonic form expect a piece called a symphony to have three or four (depending on when it was written) main sections, called movements. They expect a moment of silence in between movements, and also expect the movements to sound very different from each other; for example if the first movement is fast and loud, they might expect that the second movement would be slow and quiet. If they have heard many symphonies, they also would not be at all surprised if the first movement is in sonata form and the third movement is based on a dance.
Other kinds of music are also so likely to follow a particular overall plan that they have become associated with a particular form. You can hear musicians talk about something being concerto form or sonata form, for example (even if the piece is not technically a concerto or sonata). Particular dances (a minuet, for example), besides having a set tempo and time signature, will sometimes have a set form that suits the dance steps. And many marches are similar enough in form that there are names for the expected sections (first strain, second strain, trio, break strain).
But it is important to remember that forms are not sets of rules that composers are required to follow. Some symphonies don't have silence between movements, and some don't use the sonata form in any of their movements. Plenty of marches have been written that don't have a trio section, and the development section of a sonata movement can take unexpected turns. And hybrid forms, like the sonata rondo, can become popular with some composers. After all, in architecture, "house" form suggests to most Americans a front and back door, a dining room off the kitchen, and bedrooms with closets, but an architect is free to leave out the dining room, and put the main door at the side of the house and the closets in the bathrooms. Whether a piece of music is a march, a sonata, or a theme and variations, the composer is always free to experiment with the overall architecture of the piece.
Being able to spot that overall architecture as we listen - knowing, so to speak, which room we are in right now - gives us important clues that help us understand and appreciate the music.
Some Common Forms
- Through-composed - One section (usually not very long) that does not contain any large repetitions. If a short piece includes repeated phrases, it may be classified by the structure of its phrases.
- Strophic - Composed of verses. The music is repeated sections with fairly small changes. May or may not include a refrain.
- Variations - One section repeated many times. Most commonly, the melody remains recognizable in each section, and the underlying harmonic structure remains basically the same, but big changes in rhythm, tempo, texture, or timbre keep each section sounding fresh and interesting. Writing a set of variations is considered an excellent exercise for students interested in composing, arranging, and orchestration.
- Jazz standard song form - Jazz utilizes many different forms, but one very common form is closely related to the strophic and variation forms. A chord progression (Chords) in A A B A form (with the B section called the bridge) is repeated many times. On the first and last repetition, the melody is played or sung, and soloists improvise during the other repetitions. The overall form of verse-like repetition, with the melody played only the first and final times, and improvisations on the other repetitions, is very common in jazz even when the A A B A song form is not being used.
- Rondo - One section returns repeatedly, with a section of new music before each return. (A B A C A ; sometimes A B A C A B A)
- Dance forms - Dance forms usually consist of repeated sections (so there is plenty of music to dance to), with each section containing a set number of measures (often four, eight, sixteen, or thirty-two) that fits the dance steps. Some very structured dance forms (Minuet, for example) are associated even with particular phrase structures and harmonic progressions within each section.
- Binary Form - Two different main sections (A B). Commonly in Western classical music, the A section will move away from the tonic, with a strong cadence in another key, and the B section will move back and end strongly in the tonic.
- Ternary Form - Three main sections, usually A B A or A B A'.
- Cyclic Form - There are two very different uses of this term. One refers to long multimovement works (a "song cycle", for example) that have an overarching theme and structure binding them together. It may also refer to a single movement or piece of music with a form based on the constant repetition of a single short section. This may be an exact repetition (ostinato) in one part of the music (for example, the bass line, or the rhythm section), while development, variation, or new melodies occur in other parts. Or it may be a repetition that gradually changes and evolves. This intense-repetition type of cyclic form is very common in folk musics around the world and often finds its way into classical and popular musics, too.
- Sonata form - may also be called sonata-allegro or first-movement form. It is in fact often found in the first movement of a sonata, but it has been an extremely popular form with many well-known composers, and so can be found anywhere from the first movement of a quartet to the final movement of a symphony. In this relatively complex form (too complex to outline here), repetition and development of melodic themes within a framework of expected key changes allow the composer to create a long movement that is unified enough that it makes sense to the listener, but varied enough that it does not get boring.