He was Dionysus
As for Orpheus’ head: after being attacked by a jealous Lemnian serpent (which Apollo at once changed into a stone) it was laid to rest in a cave at Antissa, sacred to Dionysus.
There it prophesised day and night until Apollo, finding that his oracles at Delphi, Gryneium and Clarus where deserted, came and stood over the head crying: ‘Cease from interference in my business; I have borne long enough with you and your singing!’ Thereupon the head fell silent.
Orpheus’ lyre had likewise drifted to Lesbos and been laid up in a temple of Apollo, at whose intercession, and that of the Muses, the Lyre was placed in Heaven as a constellation.
Some gave a wholly different account of how Orpheus died: they say that Zeus killed him with a thunderbolt for divulging divine secrets. He had, indeed, instituted the Mysteries of Apollo in Thrace; those of Hecate in Aegina; and those of Subterrene Demeter at Sparta.
Orpheus’ singing head recalls that of the decapitated Alder-god Bran which, according to the Mabinogion, sang sweetly on the rock at Harlech in North Wales; a fable, perhaps, of the funerary pipes made from alder-bark. Thus the name Orpheus, if it stands for ophruoeis, ‘on the river bank’, may be a title of Bran’s Greek counterpart, Phoroneus, or Cronus, and refer to the alders ‘growing on the banks of’ the Peneius and other rivers.
The name of Orpheus’ father, Oeagrus (‘of the wold sorb’ apple’), points to the same cult, since the sorb-apple (French = alisier) and the alder (Spanish = aliso) both bear the name of the pre-Hellenic River-goddess Halys, or Alys, or Elis, Queen of the Elysian Islands, where Phoroneus, Cronus and Orpheus went after death. Aornum is Avernus, an Italic variant of the Celtic Avalon (‘apple-tree island’)
Orpheus is said by Diodorus of Siculus to have used the old thirteen-consonant alphabet; and the legend is that he made the trees move and charmed wild beasts apparently refers to its sequence of seasonal trees and symbolic animals. As sacred king he was struck by a thunderbolt – that is, killed with a double-axe – in an oak grove at the summer solstice, and then dismembered by the Maenads of the bull cult, like Zagreus’ or of the stag cult, like Actaeon; the Maenads, in fact, represented the Muses.
In Classical Greece the practice of tattooing was confined to Thracians, and in a vase-painting of Orpheus’ murder a Maenad has a small stag tattooed on her forearm. This Orpheus did not come in conflict with the cult of Dionysus; he was Dionysus, and he played the rude alderpipe, not the civilised lyre. Thus Proclus writes: ‘Orpheus, because he was the principal in the Dionysian rites, is said to have suffered the same fate as the god’ and Apollodorus credits him with having invented the Mysteries of Dionysus.
The Greek Myths, Robert Graves