Binary Form:
|| A || B || or || A || B A ||. Two-part form, each part a phrase group, enlarged period or phrase group. Cadence closing first part makes strong reference to the dominant or other closely related key.
Incipient Binary:
("incipient" = "almost," "not quite," "quasi") more than a period, less than a binary, a condition mid-way between a double period and a binary.
Asymmetrical Binary:
|| A || B | A ||. Second part is substantially longer than first part.
Rounded Binary:
|| A || BA ||. Return to original thematic material in second part
a "little" coda; a short closing section or "tag." Usually an extended terminal cadence or a repeated cadence brought about by a deceptive close.

Click to see diagrams of these forms.

Ternary Form:
A B A [thematic return (A) after a digression (B)]
|| A1 = Statement || B = digression || A2 = return (or reprise) ||
Three Part Patterns (not ternary)
A A' A'' series of strophes
A B C additive, through composed
A A' B
A B B'
Incipient Ternary:
(not quite a ternary) a rounded binary in which || A(R:I) || B(R) A(T) ||
cadence legend: T:I = AC in home key.
T:V = SC in home key
R:I = AC in relative key.
R:V = SC in relative key.

If the cadence at the end of A is T:I and B ends R:I or T:V, the form is a simple ternary. This is the primary distinction between an asymmetrical rounded binary and a simple ternary. An asymmetrical rounded binary is the same as an "incipient ternary"

The "true" ternary is || A(T:I) || B(T:V) A || --or-- || A(T:I) || B(R:I) A ||

Click to see diagrams of these forms.

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