Basic idea
In music theory, a basic idea is a musical idea with melodic content that is characteristic and lasts roughly 2 measures. The content is typically comprised of 2 motifs. An alternative way to think about the size of the basic idea is that it’s small enough to fit into a larger context (such as a phrase) but large enough to be broken down into other “chunks”.
Not all basic ideas are 2 measures, but they often “feel” like 2 measures – also see Real vs Notated Measures.
In many cases, the basic idea “opens up” melodically – such as an ascending arpeggiation.
In classical music, the basic idea emphasizes tonic harmony and may utilize prolongation.
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