where it can be clearly seen that the half notes at beats 2 and 3 must be spaced as if they were quarter notes since they overlap, which is obvious only because of the presence of the indication of the meter 4/4.
It seems that many books have dealt with this problem. Although it can lead to interesting algorithms, we think it is in practice a rather minor one.
In fact, each column of notes has not necessarily the same spacing and, in principle, this spacing should depend on the shortest duration of the simultaneous notes. But this cannot be established as a rule, for at least two reasons :
where it can be clearly seen that the half notes at beats 2 and 3 must be spaced as if they were quarter notes since they overlap, which is obvious only because of the presence of the indication of the meter 4/4.
Therefore, we prefered to provide the composer/typesetter with a
set of macros, the spacing of which increases by a factor of 
(incidentally, this can be adjusted) :
The size of the spatial unit (\elemskip) can be freely adjusted. In addition, MusicTEX provides a means of adjusting the note spacing according to an average number of elementary spaces within a line (macro \autolines).