Position of labels after multiple-part appogiaturas

[allorens]

Melodic appogiaturas may occur at several, if not all, parts at the same time. This brings out a couple of questions:

• if they form a logical harmony by themselves, should they be treated as melodic of harmonic (example a)? (in the example below, I'd treat them as melodic because of the appogiatura-indicating slurs)
• if they are seen as melodic: where should one annotate the following label: on the appogiatura so to respect the idea that appogiaturas happen on the harmonic beat (b1), or after, once they resolve (b2)? I'd say b2 but this may need discussion and perhaps some examples could be included in the guidelines,

a

b1

b2

(Caldara 1733: Il suo leggiadro viso from Demofoonte)