Monophony - In music, monophony is the simplest of textures, consisting of melody without accompanying harmony. This may be realized as just one note at a time, or with the same note duplicated at the octave (such as often when men and women sing together). If the entire melody is sung by two voices or a choir with an interval between the notes or in unison, it is also said to be in monophony. Music in which all the notes sung are in unison is called monophonic.
Homophony - a texture in which two or more parts move together in harmony, the relationship between them creating chords.
Polyphony - a texture consisting of two or more independent melodic voices
Song Form - varying structures of songs like ABA, AABA, ABACA, etc.
Sonata Form -a musical form that has been used widely since the early Classical period. While it is typically used in the first movement of multimovement pieces, it is sometimes employed in subsequent movements as well. Study of the sonata form in music theory rests on a standard definition, and a series of hypotheses about the underlying reasons for the durability and variety of the form.
The standard definition focuses on the thematic and harmonic organization of tonal materials, which are presented in an exposition, elaborated and contrasted in a development and then resolved harmonically and thematically in a recapitulation. Additionally the standard definition recognizes that an introduction and a coda may be present. Each of the sections is often further divided or characterized by the particular means by which it accomplishes its function in the form.
Rondo - a principal theme (sometimes called the "refrain") alternates with one or more contrasting themes, generally called "episodes," but also occasionally referred to as "digressions," or "couplets". Possible patterns in the Classical Period include: ABA, ABACA, or ABACAD'A. The number of themes can vary from piece to piece, and the recurring element is sometimes embellished or shortened in order to provide for variation.
Concerto - usually refers to a three-part musical work in which one solo instrument is accompanied by an orchestra. The concerto, as understood in this modern way, arose in the Baroque period side by side with the concerto grosso, which contrasted a small group of instruments with the rest of the orchestra. While the concerto grosso is confined to the Baroque period, the solo concerto has continued as a vital musical force to this day.
Strophic - a sectional and/or additive way of structuring a piece of music based on the continual repetition of one formal section or block. It is the musical analogue of repeated stanzas in poetry or lyrics: where the text repeats the same rhyme scheme from one stanza to the next, the accompanying music for each stanza is either the same or very similar from one stanza to the next.
A work in strophic form may be analyzed as A A A... or A A' A"...
Contrast with through-composed, where each stanza has different music, or contrasting verse-chorus form, which alternates between two sets of music (ABAB).
In modified strophic form, the pattern is varied in some stanzas.
Binary - a way of structuring a piece of music in two related sections, both of which are usually repeated. Binary is also a structure used to choreograph dance.
Rounded Binary - Rounded Binary is also:
A B A
BUT with one important distinction:

In Rounded Binary, only approximately HALF of the A material returns after the B section. Now this is important: HALF of A returns - not A half as many times! It is literally, HALF of the original A section's material (usually the latter half). So Rounded Binary is usually written:
A B 1/2A

And like Binary and Ternary, a Two Reprise repeat pattern is common:

: A :
: B 1/2A :

Ternary - a structuring mechanism of a piece of music. Along with several other musical forms, ternary form can also be applied to dance choreography. Ternary form is a three-part structure, often notated A-B-A. The first and third parts (A) are musically identical, or very nearly so, while the second part (B) contrasts sharply with it. The B section is often known as a trio.

Common Chord Modulation (Pivot Chord Modulation):

A chord that exists in two keys at the same time, the point where you modulate