Sophocles’ Thyestes plays: How many is ooo many?

Sophocles composed more than one play about the story of Atreus and Thyestes. Determining the exact number, though, is a difficult task. We know of a play with the double title Ἀτρεὺς ἢ Μυκηναῖαι, of which we possess two short fragments. Edited under the name of Θυέστης are twenty-four fragments of various dimensions, coming from different sources and, most importantly, with different supplementary epithets: if each title-variant served as proof of the existence of a different tragedy, we would have as many as five plays about the strife between Pelops’ sons: "Atreus/Mycenaean Women", "Thyestes I", "Thyestes II", "Thyestes III", "Thyestes in Sicyon". An analysis of the tradition of text titles from the fifth century BC onwards can show that this is hardly the likeliest scenario, and that there were probably no more than three Thyestes plays by Sophocles. As for the plays’ plots, a precious tool is offered by the comparison of Hyginus’ Fabula 88 and two vase-paintings from fourth-century BC Apulia: the mythographic text and the two works of art tell a tale which could have Sophocles as its ultimate source.