I'm not that much into Tool, but I've heard just about everything Hicks has done.

Talk about dark!
Funny as hell though!

He was the Lenny Bruce of our day.

Dark to me means mood, and the lyrics, if part of a particular piece of music.

My daughter is playing a zombie in her theatre production next month... I really don't like zombies... She said I didn't have to go if it was going to scare me too much, lol! (I wouldn't miss it for the world).

One of my all time favorites. Here's another. Different group...
http://m.youtube.com/watch?v=EzgGTTtR0kc...

You know that album was dedicated to Bill Hicks, right? I must confess my surprise to find anyone familiar with Tool or Hick's here though. Right on. I'm out of time tonight, but I'll try to find my favorite Hick's clip for ya tomorrow.
Great question for a post, and per your last question, I think a little dark is required for a contrast to the light, so long as one does not let it consume them.

I can't think of Tool's Aenima and not think of Bill Hicks' "Arizona Bay"
http://www.youtube.com/watch?v=vpmgO4BTN...

I must admit I have a bit of dark streak that I do well at keeping in check. Musically, I listen mostly to stuff that few here would probably be familiar with, though I prefer my darkness to have some artistic value. Here's just a couple from the top of my head.
TOOL:
http://youtu.be/JHdlhUfJ5qc
http://youtu.be/qJp2fTTvIig
http://youtu.be/_tcW-j7KFgY
http://youtu.be/2bKy57OeNU8

If you want something kinda dark, yet very smooth listening, with strong sensual overtones, any album by Morphine should set the mood. Good music to seduce a woman to. (If you're into that kinda thing)
http://youtu.be/XWKYxhyKja4 --
http://youtu.be/AnRMpIRVTUc
http://youtu.be/Q889itJ4Lr8
http://youtu.be/OirXJUQEzDM
http://youtu.be/qm2Lab-8Uto

While I like dark music, I can't say the same for most TV and horror movies. Shameless violence for the sake of shameless violence, I can do without...
That being said, I find most comedy nowadays to be anti-life in its consistent glorification of the fool and immature foolishness, that is geared towards the lowest common denominator; and in my opinion is just as bad or worse in some ways than a slasher film, though both are simply glorifying the worst in man, and therefore, wouldn't fit in with Rand's definition of good art.

I bet I've gone through 4 copies of their self titled album. Although, One of my favorite songs is 'Testify' off the album you posted.
http://youtu.be/j_zyb-XXWz0

Assuming that you mean that 'dark art" contains a substantial amount of morbidity, yes there is a place for it in an Objectivist life. One can enjoy this form of art for a temporary emotional experience without it becoming a blueprint for a life's philosophy. A popular song of the 60s, "Is that All There Is," comes to mind, applying this question to a house fire and other everyday occurrences. The message here is: "Is That All There Is To Life?" The song also states, "Get out the booze." This fits the description of a chronically depressed person, and perhaps a prelude to suicide.

I am not fond of the dark arts. I not only refuse to watch horror shows, but I sometimes find Disney too dark for comfort. I am a 'puppies and flowers' person with respect to entertainment. (Actually, 'puppies and archetypal heroes and flowers'.) The darkest I get (and it is not actually dark) is listening to Wagner whilst sprawled on the couch with a glass of Cab.

Jan
(Finally saw Capt Am, The Winter Soldier - described on prior posts, this site. OMG. A movie with content?! Content that I actually agreed with?!...saw it again the next evening. Thx for the discussion of this movie.)

The lyrics yes but the music itself didn't set the tone as dark to me. Consider Led Zeppelin singing Mary Had A Little Lamb, now that would come off as dark to me. :)

I wouldn't say dark as much as I would ominous. :)

Cool!
Keep us posted.

You didn't find any of that music dark?

I find it hard to imagine a darker song than Space Saviour, a literal love song to heroine (not the only one the band has written).

Sorry, I didn't find anything particularly dark about that music. In fact, I found quite a bit of it like commercial music in Italian films. :)

Now dark doesn't get anymore dark or dismal than this (don't cut your wrists listing to this):

Black Sabbath - http://youtu.be/B9XpxPj0lk4

Incidentally I hate the band and wouldn't listen to their music unless paid to. However, this is the the absolute darkest song I've ever heard - ever.