The gods of Greek and Roman mythology were named and described based on particular qualities or fields of rulership attributed to them. The same gods are the ones used in naming the planets. Saturn was given rulership of limits, lines, borders, extremes, and those things describing where something ended and another began. Something definable in black and white terms has Saturnian qualities. A unit of measure, even music measure would be attributed to the god Saturn.
Saturnian music is music that is held strictly to the beat or measure.
As myth has it, Saturn stole the kingdom of the earth and heavens from his father Uranus. Seeing this, Zeus split the two rulerships giving Saturn the rulership of the Earth and his father Uranus rulership of the Heavens. While the two gods have what appears to be separate realms, in fact they are always in competition. A person who sees or describes things in Earth like tones, is always able to do so in black and white, in other words with clear distinctions between opposing points, objects, or subjects. Uranus challenges the limits established by Saturn, by, let's say increasing the gray area between extremes or making the lines blurry, or difficult to perceive, on the one hand, but more revolutionary, less harsh, more feeing influenced, such as the impact of masterfully applied Rubato.