"So what does it SYMBOLISE?"

I sometimes think that this is a profoundly UnCatholic question to ask. 

Of course, as concerns the Consecrated Eucharistic Elements, the prods both inside and outside the Church will give this answer: "They symbolise Christ's Body and Blood". It may then become our duty to embark upon the laborious task of explaining yet again that the Elements ARE the Lord's Body and Blood.

But I fear that the malaise may go even deeper. My view is that the natural and the supernatural interrelate, interpenetrate, in the Liturgy, and especially during these days of the Paschal Mysteries.

Let me begin with the Oil of Chrism.

S Cyril of Jerusalem taught his catechumens that, after the invocation of the Holy Spirit, just as is the case with the the Loaf of the Eucharist becoming the Body of Christ, so (houto) this holy muron is not 'bare' (psilon)--or as someone might say 'common' (koinon)--oil, but the kharisma of Christ and, by the presence (parousiai) of the Holy Spirit is become 'causal' (energetikon) of his  Godhead. "And the body is anointed with the visible muron, while the soul is made holy by the holy and unseen Spirit."

Here comes the first of today's two funny bits.

When the 'reformers of the 1960s incorporated this passage in the Liturgy of the Hours, they chickened ... the wimps chopped out the strong parallelism between the Consecration of the Eucharistic Loaf, and the Consecration of the myrrh.

But, hey ... 

In the Traditional Paschal rites of the Roman Church, the Pontiff begs the LORD, the Holy Father, through Jesus Christ His Son, that he might deign to sanctify the richness of this creature with his blessing and to mix into it the virtus of the Holy Spirit through the power of his Christ.

Immiscere is a natural, functional term such you might find in any recipe book, such as the much-fingered 1960s volumes on our kitchen shelf.

This is what, at the Chrism Mass, our Bishop asked God to make an ingredient in the Oil of Chrism. I do not think that we are here a million miles from the instincts of S Cyril. 

And here's another thing the Bishop did. He breathed (three times) on to oil as he consecrated it.

This clearly symbolised ... er, No; it didn't "symbolise" anything.  

As Dix used to explain, the Bishop is "the mediatorial, sacrificing priest ... the unique organ of the Holy Spirit who indwells the Church ... ex officio a prophet, ex officio a healer and (the highest form of healing) a supremely potent exorcist." [Today's second Funny Bit: Dix's powerful advocacy thus assigned to (Anglican) bishops something most of them neither wanted nor for the most part believed in: the status of Sacrificing Priest and of  'supremely potent' confector of Sacraments. But Dix denied them what they were really ravenously hungry for: the Bergogliological  jurisdiction to ban and to extirpate the hated Tridentine Eucharistic Rite.]

Your Bishop at his Chrism Mass is homo mixtus Deo, the Powerful Organ of the Spirit. As he breathes on the Oil, his breath is the Breath, the Pneuma, of the creating Father (Genesis 1: 1) and of the Incarnate Lord (John 20: 22) who in this rite so empowered his disciples. It is one of the most powerful elements in the mysteries of these three mystery-laden days.

You know how universal the use is of the Oil  of Chrism. At what in the West we call Confirmation, the Bishop uses it with the words Signo te Signo Crucis et confirmo te Chrismate Salutis (and what a tragedy it was that anybody thought to tamper with those words). Ordinations; Coronations; the Blessings of Bells and of Churches ...

The Mystery of the Chrism binds together these three days, and the ancient liturgy rightly speaks of a Sacramentum perfectae salutis vitaeque; it refers to the constitutionis tuae  sacramentum, using the word Sacramentum in a broad and prescholastic sense. 

Incidentally, if we are to believe Prudentius, the Blessing of the Easter Candle, as an instance of a Lucernarium, involved the use of Chrism: Lumen ... tinctum pacifici Chrismatis unguine.