key property
The estimated overall key of the section. The values in this field
ranging from 0 to
11mapping to pitches using standard Pitch Class notation (E.g.
0 = C,
1 = C♯/D♭,
2 = D, and so on). If no key was detected, the value is
-1`.
Implementation
@JsonKey(fromJson: convertToIntIfDoubleValue)
int? key;