I am going to be the Keeper of Arcane Lore again this Saturday, and now it's prepping time. As usual it's complex. In a scenario where investigation is common, you need to have lot of information available. Not only give the characters enough rope to hang themselves by, but also enough information for the players to to feel it is a real work they are interacting with. I find this is slightly different than a game like D&D or T&T.
The idea of making the game world seem real involves sound. When our Keeper ran us through the Beyond the Mountain of Madness campaign, he made good use of sound. Ambient sound like engine sound, arctic winds or the lapping of waves can go a long way to make the players feel involved, which is something I try to do when running CoC. The coming scenario, Tell Me, Have You Seen the Yellow Sign? (from Chaosium's Great Old Ones) will be set in New Orleans. Guess what kind of sounds I'll need? I don't even like jazz music...
You know what? Right now I'm contemplating how to introduce more yellow objects into our living room, just as "background noise". I wonder why CoC always makes people go that extra mile?
It would be fun to hear if any of my readers have done something like that, or if you have run TMHYStYS?