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Borrowed chords and JSON format

I am trying to understand how the Hookpad exports chords into json format. It seems like the field “borrowed” is transcribed into signed integer: what does it exactly mean?

Thanks.

If the borrowed field is a 7-tuple, each entry represents the number of semitones of the corresponding scale degree relative to the tonic. For example, [0,2,4,5,7,9,11] is simply the major scale, [0,1,3,4,6,8,10] would be the altered scale, and [1,2,4,6,8,9,11] is what you get if you borrow a chord from Major in a Minor key then switch that key region to its relative Major. This mechanism allows chords (but not keys) to use scales entirely absent in Hookpad.