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Section 12.5 Harmonically Closed and Open Sections

A harmonically closed section ends on the tonic chord (\(\left.\text{I}\right.\)). A harmonically open section typically ends on a non–tonic chord like \(\left.\text{V}\right.\), but could also end on \(\left.\text{IV}\right.\).
In an AABA form, the A sections are usually harmonically closed, ending on \(\left.\text{I}\right.\), and the B section (or bridge) is usually harmonically open, ending on \(\left.\text{V}\right.\).
In verse-chorus form, sections that leads into the chorus (verse, pre-chorus, and bridge) are usually harmonically open, while choruses can be harmonically closed or open.
If you compose a piece in AABA or verse-chorus form, placing harmonically open and closed sections appropriately is important to the flow of the music.
For example, the verse and bridge on “We Are the World” are harmonically open (ending on \(\left.\text{V}\right.\)) while the chorus is harmonically closed (ending on the tonic chord, \(\left.\text{I}\right.\)).