Another Custom Music Problem
I didn't install them, most of the map was whitish, but you can't finish compiling if there are missing instances 
So I had to grab Skotty's bumbbleball stuffs, replace your edited elevator instances and one for the button frame...
I am unsure about if you really understood the developer mode advise, because yuo would have seen your I/O immediately, so let me explain it a little bit better:
1. Run the game
2. Open the console and enter this command:
developer 2
3. Load your map
What you got is that you will be able now to see (at the top left side of your screen) all messages for the inputs / outputs happening in your map. If you miss any, don't worry, you can check them calmly in your console too (and scroll up/down). If you read them all, you'll easily identify when is the custom ambient_generic called "music" and which entity was the one that triggered it. Or find if a any other sound was actually triggered or not, and what was the last effective output in the I/O chain, ok?
useful tools and stuff here on TWP 
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But that's exactly what I did. I saw the IO working but nothing happened to the music. I'll try compiling again to see if it works.
Alright. In the console: "An error occurred while attempting to download a file from the UGC server!
[Sound] S_StartSound(): Failed to load sound 'vobpmusicsimply think.mp3'. Can't create mixer."
And for the funnel map, the music still stops when entering and exiting the funnel even though it's put into the vo folder.
Nice music, btw. First of all about sound file path - it should be sound/vo/cavejohnson/(your file) to keep music playing while player is in a funnel (for me it works, check my last map Demonian). As for an ambient_generic's flags - you sould have first two checked and the last one unchecked. And finaly, did you update game's audio cash (snd_updateaudiocash command in the console) after you placed your file in game's folder?
Oh, and I have my music in .wav not .mp3. This way it can be looped automaticaly.
Hmm, I'll try that, thanks. (FYI, the music is from "The Hamster Alliance", made for Blue Portals OST).
All right, I'm getting nervous. Now it says "cannot find mixer" or something like that.
Well, I don't like people being nervous so I went into your problem more deeply. 
And found that problem is caused by the file name. Renaming it to "Simply.mp3" has fixed the issue. So it seems like the engine doesn't like spaces in file names.
Offtop: do you skybox and env_sun works ok?
I'm not really sure what the effects are anyways with the env_sun, but the skybox is OK for now.
Edit: Still can't create mixer.
Alright, it worked. I changed the name and rebuilt the audio cache. Now I'm going to check the funnel map. Thanks for everyone's help.
I'll just throw this out there even though the problem was solved. I find that if all the tags and outputs are correct (meaning it would work even if the sound was not custom), if I run -tools mode (go to properties and launch options), the song gets fixed into the map permanently, and will work w/o tools mode. I recommend this in the future for anyone having the same issue.
EDIT: snd_rebuildaudiocache also seems to work, if you type that in the console. (though I have not tested it)
(Granted anyone sees this)