Optionalkey?: KeyLikeThe key the tracks are read in, when it is already known.
Optionalmeters?: MeterLikeThe meter the tracks are read against, as one time signature — '6/8' or
its data — or as the map of a piece that changes meter. Naming it here and
as ts too is an input error, since the two name the same thing.
Optionaltimeline?: ChordTimelineA chord timeline to analyse against, instead of inferring one from the notes.
How an arrangement is built: the settings it is read under, with the key named any way the library names one and the harmony given as the timeline the analysis functions take.