I don’t often use CC music anymore, because I’m buddies with a composer or two. That being said, the offerings at soundimage.org are spectacular, and whenever I hear someone asking for recommendations, this is the link I whip out first.
As of me writing this article, that site alone contains over 1700 tracks of music and sound effects, all of which are high quality and free for you to use in your Visual Novel so long as you give credit to the creator, Eric Matayas. You’re also allowed to alter them as you see fit, as long as you still give him credit for the original.
The music itself is organized into categories like Horror, Corporate, and Epic/Battle. This helps you find things that match what you’re looking for quickly despite the huge amount to search through. The SFX is similarly categorized, separate from the music.
A new thing since I last used this site heavily is that there’s now art to be had as well. Game textures and background art and other such things are also up for grabs in large quantities. I can’t personally speak to their quality since I haven’t explored any myself, but if they’re anything like the audio, they’ll be quite strong.
The one caveat? It’s for SFW use only. Sorry….