Enochian magic
Enochian is presumably the language of the angels and was discovered by John Dees, or at least his scrier. Dees was a reknowned Elezibethan alchemist capable of turning lead to gold and had agreed to trade his alchemical knowledge for the services of a scryer that could communicate with angels through crystals. The scrier, whose name I've forgotten, established contact with crystals provided by Dees and developed a series of Keys.
The keys are tables of letters, some forwards some backwards, along with a series of patterned shapes to read off names of angels. The Keys became progressively larger and involved more complicated shapes. (I must confess, I could never make sense of the "pattern" in the shapes. Looked like the results of drunken Tetris to me.)
The theory was that use of Enochian would allow one to call upon the angels for various services. Since "Man is created in God's image" the angels will obey one who is pure.
IIRC this was combined with the tetragrammaton, the four-fold name of God. The four hebrew letters that make up the name of God. The letters are yod

, he (h), ve (v), and another he. YHVH ("jehova") is an interesting bit of Kabbalism with quite a few numerological tricks (the letters make the shape of a man, spell out "man + woman = family", etc).
The fundament is that God is beyond complete knowledge. The four letter name is composed of three unique letter because three is the simplest stable form (3-legged stool, triangle, etc) and we are too simple to comprehend the higher, 4th order, and see it eclipsed by one of the 3 we can perceive. This is somewhat amazing to me as it is a good explanation for a 4-dimensional being perceived by 3-dimensional entities.
Regardless, by invoking the name of God and focusing on him, the angels perceive that spark of divinity within us and obey. Each of the letters is assigned a cardinal direction and element (yod = north & air, ve = south & earth, etc). The caster gestures towards towards the elements while intoning the letters in a fashion appropriate to the task.
E.g. if trying to peacefully call an angel with an earth affinity you would first gesture southward (earthward) and intone Ve, west to Hod, east to Hod, and lastly north (air) to Yod. This is a peaceful invocation that shows the earth spirit respect. To command you would reverse the process, calling on the power of Air to overcome the non-responsive earth.
Offtopic: What results is an amazingly fast and intuitive somatic & verbal mechanism that I would love to see implemented in a computer game (mouse over the four icons in sequence, possibly with variations of right/left clicking).
For the record, the scryer was apparently never taught how to turn lead into gold and left in a huff.