Theme
A complete, recognisable musical statement, usually grown from motives
Related
A theme is a complete musical statement: it has a clear beginning, a direction and a close, and it can stand on its own, be remembered and be recognised. Compared with a motive, a theme is more like a sentence than a word; it usually contains one or more motives and organises them into a shape with momentum. Sonata, fugue and variation movements all state their theme first, because everything that follows needs that statement as a point of reference.
A theme is not the same as "the main tune". In polyphonic music the theme passes from voice to voice; in a set of variations it first exists as a harmonic frame or a bass line; in a large work it can be built from several ideas of different character. What makes it a theme is that it forms a recognisable complete statement, not that one instrument plays it from beginning to end. Once a theme is split, transposed, compressed or inverted, what remains is often material at the level of the motive.
The common misconception is to use "theme" and "motive" as synonyms, or to assume that a theme must be long. In fact the two are levels of one hierarchy: a motive is the smallest unit that can be transformed, while a theme is a complete statement built from motives; a theme may last four bars or several dozen. Another misconception is that a theme must return unchanged. Its life lies in whether it keeps its identity through variation, development and recapitulation. If material becomes unrecognisable after rewriting, it was motive material rather than a theme.
Sources
- 主题的定义、类型与在曲式中的功能，参 The New Grove Dictionary of Music and Musicians, "Theme"；本文为原创表述
Used for fact-checking only; all prose is original.