When notes start at the same time (for example chords) only 1 note can participate in determining whether the bar is complete. That note is called the main note in MusiCAD. All other trailing notes are secondary notes.
Secondary notes look different during edited: the note head turns dark gray.
The second 'note' is actually two notes. The first note of that pair (the main note) has the stem down, while the second (the secondary note) has the stem up; the result is a note with two sticks. The gray secondary note is shown last and is shown on to of the usual black note.
A rest can act as a main note, if necessary, to produce a notation like the one below:
- select note duration 1/4 with <4>
- write a rest with <r>
- add a c as secondary note of the quarter rest with <insert>
- double the duration with <F8> and point with <F6>
- in the second bar the rest is made invisible with <x>