This ritual comes from PGM XIII.934—949, entitled “As the revelator Orpheus handed down in his private note”, though for reasons that will soon become clear, I title it the “Howl of Orpheus”.  This ritual was first mentioned in this 2015 post.

As Betz notes, this text is likely unconnected to the actual Orphic tradition or to Orpheus himself: “Orpheus, the legendary Thracian singer, had by this time become famous as a revelator.  Many bogus words were attributed to him; nothing is none of this one.”  Besides the general vowel permutations, this entry in the PGM is unusual for having generally unrecognizable barbarous words of power; the words LILILILAM and LILILILŌŪ are kinda similar to the more popular LAILAM, and PHRIKS and RIKS dimly recall the Ephesian grammata (ΑSKION KATASKION LIKS TETRAKS DAMNAMENEUS AISIA).  This is certainly a different type of ritual than other entries in the Tenth Hidden Book of Moses that surrounds it in the PGM, especially with its addition of breathing and howling instructions.

At first blush, this seems to be an invocation of the highest divinity Aiōn, but in an interesting way.  Most intonation and verbalization instructions in the PGM include things like “popping sound”, “hiss”, howling “like a baboon”, barking “like a dog”, and so forth, but ritual outright tells the magus to bellow-howl.  Such deep breathing and howling will induce an altered state of consciousness, and can outright knock oneself into an ecstatic trance.  Preceding this with a period of purity and fasting, or subsisting on an Orphic diet (strict vegetarian without killing) could be recommended.  Of course, that’s just an idea, since there’s really nothing to suggest that this invocation is Orphic in any sense.

After purifying yourself and abstaining from vices and addictions, enter into a calm, stable, grounded state.  Clear the mind, still the breath, and slowly intone each of the following words with a single breath each:

ΟΙΣΠΑΗ ΙΑΩ ΟΥΕΑ ΣΕΜΕΣΙΛΑΜ ΑΗΟΙ, son!

ΧΟΛΟΥΕ ΑΡΑΑΡΑΧΑΡΑΡΑ ΗΦΘΙΣΙΚΗΕΡΕ ΩΗΕΥΑΙΗ ΟΙΑΙ ΕΑΗ ΕΑΗ ΩΕΑ ΒΟΡΚΑ ΒΟΡΚΑ ΦΡΙΞ ΡΙΞ ΩΡΖΑ ΖΙΧ ΜΑΡΘΑΙ ΟΥΘΙΝ ΛΙΛΙΛΙΛΑΜ ΛΙΛΙΛΙΛΩΟΥ ΑΑΑΑΑΑΑ ΩΩΩΩΩΩΩ ΜΟΥΑΜΕΧ

Let your spirit begin to have a fluid boundary, permitting cosmic forces permeably flow through you.  Breathe out completely, then inhale deeply from the bottom of the belly to the top of the head.  Loudly and powerfully intone the following for as long as you can:

ΑΗΩ ΩΗΑ ΗΩΑ

Cease being permeable, sealing yourself with an empty spirit.  Fill yourself up completely with breath and spiritual force, and begin to bellow-howl the next words, pushing all breath and energy out of you.

ΕΙ ΑΙ ΟΑΙ

Pull in yourself and fill yourself up with as much spiritual force as you can, tightly your eyes.

Come to me, god of gods!  ΑΗΩΗΙ ΗΙ ΙΑΩ ΑΕ ΟΙΩΤΚ

With that last word, with the “tk” sound, cough it out, take a deep breath from the belly up to the head, and let out a roaring, howling bellow as loud and long as you can, letting out whatever last air remains in your lungs with a sigh-hiss.

The incantation, with the barbarous words transcribed into Roman script:

OISPAĒ IAŌ OUEA SEMESILAM AĒOI, son!

KHOLŪE ARAHARAKHARARA ĒPHTHISIKĒHERE ŌĒEUAIĒ OIAI EAĒ EAĒ ŌEA BORKA BORKA PHRIKS RIKS ŌRZA ZIKS MARTHAI ŪTHIN LILILILAM LILILILŌŪ AAAAAAA ŌŌŌŌŌŌŌ MŪHAMEKH

AĒŌ ŌĒA ĒŌĀ

EI AI OAI

Come to me, god of gods!  AĒŌĒI ĒI IAŌ OIŌTK