This document explains the left-hand keyboard of a compound bass accordion: a brief history, the range of basses and chords, preconceived chords, where they come from, how they are arranged on French and Stradella keyboards, and their notations. The realization of enriched chords, complete dominant 7th, complete diminished 7th, major 7th, minor 7th, sixth, etc., is described for both keyboards. Exercises are suggested.
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