Whilst Herodotus (450 =420 BC) was in Egypt he noted that corpses were never buried in woollen cloth or clothing and wrote of the Egyptians:
 "In this respect they agree with the rites which are called Bacchic and Orphic but are really Egyptian and Pythagorean"
Herodotus also tells us that the cult of Dionyos was brought to Greece by the black footed Melampos:
"Melampos was the one who taught the Greeks the name of Dionysos and the way of sacrificing to him and the phallic procession; he did not exactly unveil the subject taking all its details into consideration, for the teachers who came after him made a fuller revelation; but it was from him that the Greeks learned to bear the phallus along in honor of Dionysos, and they got their present practice from his teaching" 
Melampos had learnt the art of divination and oracles from the Egyptians.

Diodorus Siculus, writing between 60 and 30 BC describes the treatment of the dead in Egypt:
"When the body is ready to be buried the family announces the day of interment to the judges and to the relatives and friends of the deceased, and solemnly affirms that he who has just passed away — giving his name — "is about to cross the lake."  Then, when the judges, forty-two in number, have assembled and have taken seats in a hemicycle which has been built across the lake, the baris is launched, which has been prepared in advance by men especially engaged in that service, and which is in the charge of the boatman whom the Egyptians in their language charon. For this reason they insist that Orpheus, having visited Egypt in ancient times and witnessed this custom, merely invented his account of Hades, in part reproducing this practice and in part inventing on his own account"

Herodotus and Diodorus recognise Dionysos and Orpheus in the fertility rituals of Min and the religion of Osiris the dead king, who is the green power within the earth to revivify.

Osiris dies but never dies.

He exists beyond, immanent within the earth.

In one reading of the myth, when Persephone leaves the upper earth, nothing grows, not because Demeter grieves but because the life-work (the restoration)  must take place in the invisible, Great Below.

In Greece, rather than creating a new cosmology it leads to a  mystical interpretation of a pre-existent Greek mythology.

In the Homeric tradition gods make mistakes and have ill thought out wishes and desires. In the Orphic tradition gods are other.

They seem to represent forces, and are closer to the idea of emanations.

Understanding of the gods is experiential, the Mysteries are, from an Orphic point of view, attempts to enable an understanding beyond understanding.

Basically the experience of the Mysteries enable the student to progress towards enlightenment.

Another influence on what was to become Orphic tradition, came from Crete hidden in the word used for both Zeus and Dionysos: Zagreus.

The Ionian Greek word zagre signifies a hunter, and a zagre was a "pit for the capture of live animals".

From this derivation the name Zagreus adds a cthonic, underworld dimension to which ever deity it is given- in Orphic myth we have- Dionysos Zagreus-Dionysos who captures or ensnares.

Nietzsche interpreted Dionysos Zagreus as Dionysos the hunted, not the hunter, and defined the terifying and horrific, tearing apart as both a literal and psychological aspect of the cult of Dionysos.

Persephone in Orphic theogeny.
According to W.K.C Guthrie- Orpheus And Greek Religion there are two main sources for the Orphic Persephone myth:

1/ Clement of Alexandria  (AD 150-.211), and

2/ The alter of Hyakinthos at Amyklai.

Clement wrote several religious essays called: The Exhortation to the Greeks. In book one you can read that Zeus, Persephone's father organises the abduction of his daughter and then, in the form of a serpent creeps down into the underworld to have intercourse with her:

Zeus becomes the ravisher as well as father of the maiden, meeting her under the form of a serpent, his true nature being thus revealed. At any rate, in the Sabazian mysteries the sign given to those who are initiated is
"the god over the breast"; this is a serpent drawn over the breast of the votaries, a proof of the licentiousness of Zeus. Persephone also bears a child, which has the form of a bull. To be sure, we are told by a certain mythological poet that The bull begets a snake, the snake a bull; on hills the herdsman bears his mystic goad,the herdman’s goad being, I think, a name for the wand which the Bacchants wreathe.
Would you have me also tell you the story of Persephone gathering flowers, of her basket, and how she was seized by Hades, of the chasm that opened in the earth, and of the swine of Eubouleus that were swallowed up along with the two deities, which is the reason given from the custom of casting swine into the sacred caverns at the festival of the Thesmophoria? This is the tale which the women celebrate at their various feasts in the city, Themophoria, Scirophoria, Arretophoria, where in different ways they work up into tragedy the rape of Persephone.
Zagreus became Sabazios  because both words sound similar?

Sabazios was originally a Phrygian deity portrayed as a nomadic horseman god, wielding a staff of power.

Much latter the C10. A.D Byzantine Greek encyclopedia, Sudas, explains:

"Sabazios... is the same as Dionysos. He acquired this form of address from the rite pertaining to him; for the barbarians call the bacchic cry 'sabazein'. Hence some of the Greeks too follow suit and call the cry 'sabasmos'; thereby Dionysos [becomes] Sabazios. They also used to call 'saboi' those places that had been dedicated to him and his Bacchantes... Demosthenes [in the speech] 'On Behalf of Ktesiphon' [mentions them]. Some say that Saboi is the term for those who are dedicated to Sabazios, that is to Dionysos, just as those [dedicated] to Bakkhos [are] Bakkhoi. They say that Sabazios and Dionysos are the same. Thus some also say that the Greeks call the Bakkhoi Saboi
I can't find any images of the alter of Hyakinthos.

W.K.C Guthrie also says that Euripides play, Helena (the one in which the real Helen of Troy is spirited away to Egypt and Paris abducts an illusion) is another source of the Orphic idea that Zeus father's Dionysus with his own daughter.

The Orphic version of Persephone's story.
Begins with the abduction, but this time from Eleusis.

It is the sun that tells Demeter that Hades has taken her daughter.

Demeter is entertained by Baubo (of the lewd jokes) in the house of Dysaules (ill-housed); their sons are Eubuleus, Eumolpus and Triptolemos who also tell Demeter of the abduction;  they say that they saw Persephone taken as they were out, tending their herds.

Clement of Alexandria says it is Eumolpus (who begins the Eleusinian mysteries).

Zeus creeps down into the underworld in the form of a snake and seduces Persephone. The child is Zagreus, the first-born Dionysus.

The child had horns and came into the world wearing a crown of snakes.
Nonnus, Dionysiaca 6. 155 ff
Ah, maiden Persephoneia! You could not find how to escape your mating! No, a drakon (dragon) was your mate, when Zeus changed his face and came, rolling in many a loving coil through the dark to the corner of the maiden's chamber, and shaking his hairy chaps he lulled to sleep as he crept the eyes of those creatures of his own shape who guarded the door. He licked the girl's form gently with wooing lips. By this marriage with the heavenly drakon, the womb of Persephone swelled with living fruit, and she bore Zagreus the horned baby, who by himself climbed upon the heavenly throne of Zeus and brandished lightning in his little hand, and newly born, lifted and carried thunderbolts in his tender fingers

Zeus's wife, Hera hates the child and so she allowed the Titans into the room where the baby Dionysus was playing. The Titans had smeared their faces with white clay to make them look round, they gave him a thyrsus (a fennel stalk) in place of his sceptre.and they fascinated the child by showing him his own reflection in a mirror....until they could get close enough to tear him to pieces (the original bull sacrifice embedded in the image of the worshippers of Dionysus ripping live animals apart).

When Zeus discovered the crime he blasted the remains of his child and the Titans with thunderbolts and locked the Titans into the deepest dungeon of the underworld. Then he took the heart of Dionysus and gave it to Semele in a drink, thus she became pregnant with Dionysus.

Meanwhile humans were formed from the ash of Titan and God which accounts for our need for rituals of purification and our time of punishment in this world- by living an Orphic life and avoiding bloodshed and murder, humans may pay the penalty for the ancient grief the Titans caused Persephone, and achieve freedom.

The baby Dionysus now safe in Semele's womb cannot remain hidden from Hera who once more intervenes and tricks Semele into causing Zeus to appear to her in his real, god-form. She is blasted by the heat and light and killed instantly.

Zeus took the unborn baby and sowed him into his thigh.

So it is that Dionysus is twice born.