I was so young I don't remember, but given how young I was it probably wasn't his actual stories.

For CH soundtracks, there's of course the Bloodborne OST, as well as some of the fan songs based off of it (A Thousand Eyes by Miracle of Sound, Summon the Choir by Aviators. Aviators also has the songs "Dreams of the Deep", "The Wall of Sleep", and "Can you Hear It?", which are directly based off of Lovecraft). As well as that, there's a song called "Unworthy" from the retro fps DUSK (highly recommend playing the games, by the way), as well as the ambient music made by an artist called Cryo Chamber. For metal, there's like four Metallica songs based off of the mythos (Those are "The Call of Ktulu", "The Thing That Should Not Be", "All Nightmare Long", and "Dream No More").The Vision Bleak is a band with a good chunk of CH themed metal, my personal favorite they made is "The Shining Trapezohedron". There's a few misc songs I dug up through an autogenerated Spotify playlist: The Dreaming City and Into the Deeps, both by a small band called Centregaze, In the Court of the Dragon by Trivium, The Silver Key by Dark Moor, and a band called Arkham Witch. Venturing into the goofier side of mythos themed music, there's "Cthulhu" by Grailknights, Fodder for the Elder Gods by 2000s-2010s goth band Creature Feature, if you've heard of them, there's Fate of the Stars by Tally Hall, and there's an entire Psychobilly band called The Darkest of the Hillside Thickets that makes mostly Mythos themed songs. There's probably a bit more, but that's all I could think of/find in my playlists. (Yes, I do listen to a lot of music lol)