Ligatures.
Neumes are always used syllabically; a three-note neume, for example, indicates that (at least) three notes are to be sung to a single syllable. The single-note neumes indicate that only a single note corresponds to that syllable.

Technically, two or three-note neumes are designed as ligatures, so when typing the single-note neumes without spaces in between, the correspondent glyph is automatically substituted (see above).

Contextual alternates.
A system combining stems and neumatic elements through contextual substitutions has been thought to obtain up to six-note neumes.

Above, you can see the contextual substitution of the bar. Depending on "the context" its length can considerabilly change.

In some cases, ligatures are also used to obtain one-note neumes, which could not find their place on the keyboard. ‘Virga’ for example, is the combination of ‘punctum’ (A-M) and the letter ‘V’, which will never be seen, but is necessary for the substitution.

When necessary, extra-spacing between glyphs is obtained with contextual rules, and not with kernings. The glyph is automatically replaced with an identical one, designed with a bigger left side-bearing.

Exception rules for substitutions have also been set; with zero-width characters it’s possible to avoid ligatures, to add extra-spacing, to position rhythmical marks. The example shows the (invisible) character “!” used to break the first ligature (F+G) in order to apply the second one (G+H).