sequential durations should provide spacers

[Levitanus]

If Music(Note('c'), Duration(2), Duration(1)) — there will be written c21

[wbsoft]

If you want separate durations as unpitched notes, use Unpitched. E.g.

>>> from quickly.dom.lily import *
>>> n=MusicList(Note('c', Duration(1/2)), Unpitched(Duration(1)))
>>> n.write()
'{ c2 1 }'