—  Arithmetic,  Geometry,  Music, and  Astronomy.
The Quadrivium (which pertains to Matter & Quantity)- the advanced four.
 MUSIC OR HARMONIC THEORY —Number in time.
The Quadrivium with Gene Odening, Gnostic Media Podcast episode #050 (start here)
Quadrivium – Number, Geometry, Music, & Cosmology with John Martineau, Gnostic Media Podcast episode #103 (intermediate)
The Elements of Music with Dr. Jason Martineau, Gnostic Media podcast episode #109 (advanced)