My understanding of allomorphy, is that it is the case where a single functional morpheme is realized with many different Vocabulary Items.
But homophony (that is accidental) is also found with Roots, for instance, bank could mean side of a river or financial institution, which have identical phonological representations but have no related semantic meanings.
My question is to what extent the two entities that have the same phonological forms are semantically related so that they could be classified into allomorphy.