Assertion: bass's note | /r/HasProperty | range of a major seventh
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Source sentences:
text: A free-bass system is a system of left-hand bass buttons on an accordion, arranged to give the performer greater access to playing melodies on the left-hand manual of the instrument and to forming one's own chords, by providing a buttonboard of single-note buttons with a range of three octaves or more, in contrast to the standard Stradella bass system which only allows bass notes (range of a major seventh, from C to B) and preset major, minor, dominant seventh, and diminished chords (for the preset chord buttons, pressing a single chord button sounds a three-note chord).