late but some contemporary writers, may still be useful:
Athenaeus outlines events
Pausanias: “A choir of boys … accompanied by the flute, sang the praises of [Apollo].”
Pausanias: “at the Hyakinthia, before Apollo’s sacrifice, they pass through a bronze door to dedicate the offerings
of a divine hero to Hyakinthus in this altar.” (Amyklaion)
Xenophon: “The Amyclaeans invariably go back home to the festival of the Hyakinthia for the paean to Apollo,
whether they chance to be on a campaign or away from home for any other reason.”
Herodotus: “their chief concern was to give [Apollo] his due.”