ANTECEDENT (weak or open) CONSEQUENT (stronger or closed)

Asymmetrical – a period in which the phrases differ in length.
Symmetrical - a period in which the phrases are the same length.
Parallel – a period in which the musical material is almost exactly the same.
Contrasting – a period in which the phrases have differing musical material.
Modulating – a period in which the Consequent phrase modulates.
Cadential extension – the addition of musical material beyond the point at which a
cadence is expected.
Elision – the cadence point of one phrase becomes the beginning of the next phrase
(overlap or dovetail).
Interpolation – the repetition of a phrase becomes longer by the insertion of new
material not heard in the original phrase.
Double Period – phrase 1 and 3 are often identical or very similar.
Phrase 1 -------I.A.C. Phrase 2 -------- H.C. Phrase 3 ------I.A.C. Phrase 4 -------P.A.C.

Phrase group – NOT a period structure. Groups of phrases that end with weak cadences
H.C. or I.A.C (Transitional and Developmental functions),

Cadential Phrase Group (or Closing section) - groups of phrases that end primarily with
P.A.C. (Cadential function).