When I was originally doing research to develop an esoteric musical framework for the Pegataur Working, my initial line of questioning was primarily concerned with finding a way to map musical theory to hermetic or occult philosophy.  While it wasn't ultimately detailed enough in the low-level way I was looking for, I did stumble across an interesting bit of old world thinking about the Music of the Spheres.

If you're not familiar with the Music of the Spheres, this is a concept closely tied to the Old School pre-heliocentric worldview.  Basically, the heavenly hiearchy, with Earth at the center, of course, was thought of as a divine symphony that actually created a harmonius soundtrack for the universe.  As the Greeks had discovered some time ago, there were mathematical formulae underlying the divisions of tones into scales, and calculations about fret-spacing on the neck of stringed instruments that could be used to develop tonally accurate instruments.  It isn't a far stretch to take Pythagorean mysticism and combine it with a Western religious and scientific worldview and superimpose this earthly knowledge onto the heavens.  This is literally consistent with the old Hermetic axiom "As above, so below."   

In 1531, Heinrich Cornelius Agrippa von Nettesheim's released Book II of The Three Books of Occult Philosophy.  In this massive treatise on the natural (occult) sciences, Agrippa penned Chapter 26, "Concerning the Agreement of Them with the Celestial Bodies, and What Harmony and Sound is Correspondent of Every Star" that perfectly summarizes the Neoplatonic and Renaissance thinking of the time about this issue.  It is most pleasantly given in the form of poetry, in which each of the planets are given a classical muse as well as a mode:

Silent Thalia we to the Earth compare,
For she by music never doth ensnare;
After the hypo-Dorian Clio sings,
Persephone likewise doth strike the bass strings;
Calliope also doth chord second touch,
Using the Phrygian; Mercury as much;
Terpsichore strikes the third, and that rare,
The Lydian music makes so Venus fair.
Melpomene, and Titan do with a grace
The Dorian music use in the fourth place.
The fifth ascribed is to Mars the god
Of war, and Erato after the rare mode
Of the Phrygians, Euterpe doth also love
The Lydian, and sixth string; and so doth
Jove.
Saturn the seventh doth use with Polymny,
And causeth the mixed-Lydian melody,
Urania also doth the eighth create,
And music hypo-Lydian elevate.

If you're familiar with music theory, you can probably understand this about 50% of the way, and then, unless you're familiar with Gregorian chants and medieval music theory, you will see reference to some odd sounding modes here that you had never heard of before (e.g., hypo-Dorian, hypo-Lydian).  According to the editor's comments in my edition of Agrippa's Three Books of Occult Philosophy:

The ancient Greeks used six modes...coresponding more or less to the modern keys...Departure from these modes was resisted as an anti-intellectual pandering to the mass appetite for pleasure.  The names of the Greek modes were preserved in the system of church music known as plainsong, or plain chant (Gregorian chants), established in the 6th century by Gregory the Great, although these differed completely from the Greek.  Others were added for a total of 14, of which two-the 11th [Locrian] and 12th [Hypolocrian]-are never used because they are impractical.  Agrippa would have been familiar with this system.

This presents a new challenge in mapping an ancient system to modern musical theory: modern musical theory has 7 modes, while musical theory at the time of Agrippa's writing was working with a total of 14 (in theory, and 12 in practice), having twisted 6 classical original Greek modes plus an additional 8, minus 2 due to the "impractical" nature of the Locrian and Hypolocrian modes (an idea that persisted until the birth of Jazz, by the way, when the diabolus in musica, the old nasty tritone, was no longer off limits to musicians - welcome to the birth of the modern age).

Let's take a moment to translate this into modern musical terms.  If you need a refresher on your modes, here they are again with their chord correspondence relevant the major scale based on the Ionian mode of any given key:

• Ionian (I: major)
• Dorian (ii/minor: flat 2, 7)
• Phrygian (iii/minor: flat 2, 3, 6, 7)
• Lydian (IV/major: sharp 4)
• Mixolydian (V/dominant: flat 3)
• Aeolian (vi/minor: flat 3, 6, 7)
• Locrian (vii/diminished: flat 2, 3, 5, 6, 7)

At a first pass of just replacing Gregorian for modern mode substitutions (based on the intervals in the Gregorian modes), laid out in the old order of the planets from the Moon (innermost planet from the Earth) to Saturn (the outermost planet), we wind up with the following:

Other interesting occult attributes that Agrippa gives for the planets are as follows:

Although I didn't initially find this useful, the ancient wisdom presented here is rife with potential for artistic, musical, and magickal projects.  There are also several interesting things that I notice when I look at the data presented in this manner.

The first is that under the Gregorian system of music theory, the Dorian mode was essentially the beginning of the cycle, or the first mode or tonic of the typical scale.  In modern music theory, the Aeolian is the first mode of the (major) scale.  In Agrippa's system, Dorian coresponds to the Sun - making the Sun the beginning of the cycle - or the "center" of the musical universe in relative terms - even though at the time the Earth was considered the center of the universe.  

It seems entirely possible to me that the magicians, court astrologers (forefathers of modern astronomy), and other Renaissance thinkers may have been slowly working out a heliocentric model of the universe before the scientific and mathematical concepts were evolved enough or the political timing of openly challenging a Church-defended geocentrism was right.  This would not have been inconsistent with the transmission of scientific ideas coded in esoteric terms, as frequently happened within alchemy (the precursor to modern chemistry).  This is purely speculation on my part, but I like to entertain the possibility.  After all, Agrippa was a contemporary of Paracelsus and a predecessor in a long line of proto-scientists and men of learning in the tradition of Dr. John Dee, Robert Fludd, and Giordino Bruno.  Even Copernicus, who put forth the scientifically (as opposed to esoterically) revolutionary heliocentric theory of the solar system, while not explicitly an occultist, was familiar with the tradition and its ideas:

Among the ancient authorities cited by Copernicus in support of his theory was Hermes Trismegistus.  Hermes has admittedly a very minor place in the De Revolutionibus; he is one of several authorities fleetingly referred to by Copernicus, and they all appear only in order to supplement more strictly scientific arguments  It has been argued, however, that the mystical heliocentrism of Hermeticism prepared the way for the astronomical heliocentrism of Copernicus, and it is certainly true that the occult philosophers developed a high opinion of the sun.  Not that astronomical heliocentrism was universally accepted by those who espoused a solar mysticism, at least before the later seventeenth century.  A combined mystical and astronomical heliocentrism, however, was clearly more consistent than a combination of geocentrism and solar mysticism.  Whatever the impact of the occult philosophy on astronomy, in this sense we might agree with Nabil Matar that 'the victory of heliocentrism marked the consolidation of the hermetic tradition.' --B.J. Gibbons, Spirituality and the Occult: From the Renaissance to the Modern Age, 2001.

I also find it interesting that the planets were not simply assigned modes in the same order from the same starting point.  For example, you might expect to see Dorian attributed to the first planet, the Moon.  However, if we ignore the Gregorian/modern naming conventions and equivalencies, and just work off of the actual tonal qualities and emotional impact that these modes are typically thought to have, it makes sense that they are attributed where the are.  For example, Venus, the goddess of love, is attributed Hypo-Lydian/Ionian, the equivalent of the default major (and therefore most harmonious) scale in modern Western music.  Venus is also attributed with harmony and specifically that of the fifth interval - the I-V interval combination being the "power chord" on the guitar and one of the most perfect harmonies under any circumstance in every mode but one (the Locrian, which was traditionally avoided).  Even though the starting points are not in parity where you'd expect them to be, they are both still consistent in their respective cycles.  This is a fascinating artistic judgment.

Another interesting thing is that he gives to Saturn the character of "sad, hoarse, heavy, and slow words, and sounds."  Saturn corresponds to the Mixolydian mode, which is the mode related to the Dominant 7th chord and the one you would solo over a blues tune with, strictly speaking (at least jazz players probably would; in practice, most people would use some type of pentatonic scale derived from this mode).  This chord is central to Jazz and the Blues in common chord progressions, like the classic "ii-V-I" 12-bar blues progression.  The resolution of the tritone (the flat third against the major seventh) in the V7 chord to the I chord in any key is one of the most perfect resolutions.  It is somehow fitting that Jazz and its derivative, the Blues, were created by the descendants of African slaves in the United States at the turn of the 20th century, and whose "melancholy" and earthy voice of Saturn contributed to the birth of one of America's uniquely American art forms.  When I think about the world of the Gregorian chant, dominated by what to modern ears is a minor mode (Dorian), from which Agrippa's system sprung, I find it compelling that one of the newest forms of music that revolutionized the world of music was another "heavy" and often "sad" type of music.

It's funny to me that Agrippa also attributes Mars and the Phrygian mode to "rough, sharp, threatening, great and wrathful" sounds.  When this mode has its flat 3rd raised again to a major third, this mode, now a Phrygian dominant scale, is also known as the "Spanish" mode and as we all know from cultural stereotypes, Latin blood is reported to be quite fire-y (yes, my tongue is planted firmly in my cheek there).  You may recognize the sound of this mode from the "gypsy" music of the Doors and the Jefferson Airplane song "White Rabbit."  The Lizard King is wrathful, indeed.