Monday, July 22, 2013

Thematic design and phrase structure

Thematic design and phrase structure


Part I - Thematic design
The 'theme' in music usually refers to the principal melodic lines.   The tonal motion towards cadences is supported by the presentation and completion of thematic ideas.  A phrase is usually notated with a slur:

Fig.1 Slur

Part II - Motives and themes
A musical motive is a short melodic idea categorized by rhythm, contour and interval succession.  a theme is a sequence of motives that make a cohesive whole.  Motivic analysis usually entails the identification of motives and their recurrences.

Part III - Models of Phrase and structure
  A common model of phrase structure is a sentence.  A sentence is a phrase comprised of a statement, followed by a repetition, then a continuation that leads to a cadence.  The three parts of a sentence are normally in the proportions 1:1:2 (in measures) or multiples thereof.  The proportions are the defining characteristic of a sentence.
Another type of phrase is the period.  The first phrase in a period leads to a weak cadence (IAC or HC).  This first part of the period is known as the antecedent.  The second part of the period, known as the consequent, leads to a strong cadence (usually a, AC of some sort.