You can probably find ample good reviews of this set online, since this is an early Blu-Ray edition from the essential Criterion Collection, and is a lush and perfect enough package to have received awards. I purchase very few movies on disc, in spite of being a rabid cinephile; and this is one BR set that I bought _without hesitation_. Describing some of the films might sound like parody, insured boredom, or unbearable pretense, but I'm telling you....experiencing the films is something else. Theoretical baggage is posterior to the immediate, sensual experience of the films, as they unfold. Brakhage was a magician of some kind, a sui generis artist.
Listening to music while watching these silent film-paintings (even the ones that are not hand painted, as are his later films) is probably fine, but I'd personally suggest trying (and trying....and trying...) them in silence, the way he intended them to be seen. The effect is, I think, an intensification of the experience, since (if I'm correct) SB intended the films to BE A FORM OF MUSIC, or at least to be very much like music, in its essence. I've done this with friends, sometimes several hours at a time, and the effect is not just in my own head; others concur, and even bring it up afterwards without me prompting them.
The only other thing I might suggest is going out of your way to see these on celluloid if you can, while celluloid and film projectors still exist. And while these particular films still exist, _as_ films, which might not be for terribly much longer. It really is a different experience. I know, I know...isn't it always? But with many of these works, maybe all of them....it's really, really a different experience. It will shake you.
Critic Fred Camper, a sensitive and humble writer on many kinds of film art, has written extensively on Brakhage (including notes in this DVD/BR edition), and his website is a valuable resource. Also amazing is Brakhage's own short-lived radio show, which you can hear on Ubuweb. It is wonderful to hear the man speak! He's a mystic, but not a flake. And not drunk on himself, just honestly intent on, well, breaking through something to something else. How else to say this?