TwinNote TD is an alternative ‘traditional duration’ version of TwinNote. It uses hollow and solid notes to indicate duration as in traditional notation making it fully consistent with traditional rhythm notation. This would make it easier to learn both systems and use them interchangeably.
Source: Paul Morris, December 2009. (TwinNote TD was known simply as “TwinNote” during 2010, before Morris switched to the current name in early January of 2011. In March of 2011 Morris shifted the note positions up by a semitone to make C D E F G A B correspond with the lines and spaces of the traditional treble staff (instead of just C D E).)
Website: TwinNote Music Notation
Manuscript paper: Discontinuous Staves Continuous Staves