How should one describe that some solfege notes rhyme or perhaps share the same role?
The two examples are do and so (I and V) and mi and ti (III and VII).
C D E F G A B (I) (II) (III) (IV) (V) (VI) (VII) do re mi fa so la ti
The V is harmonically closest to the I, so it almost sounds like a resolving scale if one plays C,D,E,F,G.
Is the role of III and VII similar in that they are harmonically the 'middle' notes between I and V and V and the following I?
In other words the III and VII are harmonically the next closest notes to the I (or the V).
Is this why they have rhyming names? Is it to demonstrate the (diatonic) hierarchy of harmony?