Outside of Metal;
Classical = anything dark/brooding and/or meloncholy (that includes Karnatic, Ottoman, Medeival, Renassance, Baroque, and some Gagaku... Prog Rock = Opeth and Akira Yamaoka... Darkwave prog/expirimental = That would be the Silent Hill tracks... Dark Ambiance = Coph Nia Acoustic = October Falls Blues = Only bits and peices from a long lists of old blues performers...
Outside of Opeth;
Opeth, Arsis, Iced Earth, Armoured Saint, Mastodon, Amon Amarth, Arch Enemy, Darkane, Noumena, Farmakon, Blu Infinito, Novembre, At The Gates(First album only), Daylight Dies, Darkthrone, November's Doom, Candlemass, The Funneral Orchestra, Cathedral, My Dying Bride, BloodBath, Samael(various songs here and there), Metallica, Morbid Angel, Callenish Circle, Construcdead, Enter My Silence, Impious, Infernal Method, Koldborn, Withered Beauty, Vehemence, Soul Demise, Thorium, Demilich, Gorguts, Necrophagist, Psycroptic, Amaran, Unmoored, Illogicist, Nightshade, Demigod, Requiem, Aeternam, Abed, CalmSite, Devanic, Funerus, Gargaryss, Herald, Infernal Angels, Isthar, Kaamos Kalopsia, Lost Soul, Mahavatar, Mausoleia, Nephasth, Oppression, Manegarm, Pyaemia, Rapture, Souledge, Vespirian Sorrow, Pathogen, Agolloch, YTO, Abhorer, Apathy, Beheaded, Beknighted, Belfegor, Cianide, Affinity, Immolation, Halcyon, Sinners Bleed, Gorerotted, Vicious Art, Hate Eternal, Gorgasm, Mortician, Death, Mayhem...