Music and visual arts have a lot in common. Few points of similarity are worth mentioning:

Rhythm: duration / length / frequencies, including and forming (or formed by) negative spaces / pauses / absence / silence - all are common to both fields.

Proportions: harmonic proportions and their derivatives, commonly described in mathematical terms, starting with very basic, discovered by Pythagorean specifically on the acoustic / musical territory, and then going further to the Fibonacci Series having their limit in the irrational Golden Ratio.

Temperature: the temperature (cold / hot) of sounds and colours. Yet this is still considered to be controversial, it is obvious that sounds and colours can be warmer or cooler. Less obvious is an exact scientific correlation between them.

Movement: ascending, descending, elliptic movements etc. Musicians do not need an explanation of this, and neither do artists.. 

All of the above notions are familiar to both musicians and visual artists, are they not?

We can talk about background sounds and colours, we could mention intensity and saturation of the tones in the both fields... On the human capacity to see sounds and hear colours I would recommend reading about Vasiliy Kandinsky Synaesthesia as well as some modern studies.

Music, which is very abstract, and musicians with their beautiful instruments, who are so "real", are perfect subjects for my exercises.