Some fascinating and evocative music here - both suited to the nature of the game for which it was written and - being original compositions - something that will not distract players from the matter in hand as they identify music they already know.
The first track is a scene-setter, to get players into the mood for the game. If you have trouble getting your group to stop chattering and focus at the start of a game, you could use this track as an indication of "Now we are starting to play..." It's often beneficial to set limits like this, demarcations between everyday life and the alternate reality of your role-playing. (Or is this the teacher in me talking?)
Next is one billed as a 'pulp' theme - excellent melodramic stuff that should get everyone on the edge of their seats ready for whatever surprises you have lined up. Good to use as an alternate start or if you think people are beginning to drift... or perhaps as a mood-changer when you go from one of the more investigative bits to an action scene.
The track 'Ruminations' is a thoughtful piece, and aimed at those investigative scenes, or for while the characters are trying to sort out what all the hard-won evidence actually means and what they are going to do about it. It conjures up a misty and slightly menacing night, and could be used to equal effect when the characters are sneaking around not knowing just what they are going to find.
The final piece is intended for the moment it all falls into place. It somehow manages to combine spooky with inevitable and almost peaceful... even if things in any game with 'Cthulhu' in the title are anything but peaceful and never the way things Ought To Be! It's quite cinematic, so should work well if you like a dramatic finale.
As always, I'm as likely to listen to this as inspiration when writing adventures as to actually play them during a game, but then I don't like background music in films unless there's a band of musicians in shot!
[4 of 5 Stars!]