Sagibelius is a plugin for Sibelius notation software to allow notation in Sagittal – which is an extremely flexible generalized microtonal notation. Jacob Barton developed this software and more details – plus software download – can be found at this link.
I tested it on Sibelius 6.2.0 with Vista 64 and it worked perfectly. For Windows users the procedure is:
The Sagibelius font gets installed in control panel / fonts (drag and drop into the font window.)
Then find the plugin is put into the Sibelius plugin folder, in my case
C:\Program Files (x86)\Sibelius Software\Sibelius 6\Resources\en.lproj\Plugins
and put the .plg files into the Accidentals folder
C:\Program Files (x86)\Sibelius Software\Sibelius 6\Resources\en.lproj\Plugins\Accidentals
You enter microtonal accidentals through the plug-ins drop down: Accidentals / Add Sagittal Accidental.