Background music and arpeggios when flying though the air...
How I do I get background music kinda like the coop and have it create an arpeggio to whatever chord the background music is playing... It's really cool and I can't find anything on it I hope you guys know what i'm talking about...
env_soundscapes or ambient generic
If you mean the music when you are catapulted... its a trigger that enables after you get catapulted.
PortalStories.com
"Oh, in case you got covered in that repulsion gel, here's some advice the lab boys gave me: DO NOT get covered in the repulsion gel."
I think he's talking about the music thingies that happen when you're sailing through the air, majestically, like an eagle, piloting a blimp. Like in the cave johnson aera for example?
Some of the music automatically plays those tunes depending on what track is being played. Ex. Some Wheatley Chamber Music may make tunes when inside a funnel or sliding or bouncing on paint.
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They're soundscripted as far as I know. However I remember that the sync is done somehow with VScripts.
I have no idea how, though.
@ BobbyJEL101:
I think what you are looking for was well explained by Neco at the "Mapping Tips and Useful Links" thread (http://forums.thinking.withportals.com/mapping-help/mapping-tips-and-useful-links-t468-15.html). As follows:
Create your own fade-in/fade-out logic_relays and let them trigger your desired sound files when 'start_touching' or 'end_touching' the area defined by the trigger_multiple.
The trigger_multiple method also has also the advantage to be exactly a large as the room if desired.
Hope that helps!
useful tools and stuff here on TWP 
[spoiler]
[/spoiler]http://www.youtube.com/watch?v=4h_GwIo48Gw&list=UUU6OYK-SJQVoF5_hiADf09g&index=18&feature=plcp
Skip to around 1:00 and listen when he jumps on the repulsion Gel.
That sounds like it some sort of script. Might have ripped it from the blue gel chamber supplied with the sdk.
PortalStories.com
"Oh, in case you got covered in that repulsion gel, here's some advice the lab boys gave me: DO NOT get covered in the repulsion gel."
At least the laser music script is found at vscripts/laser_target/musical_laser_catcher.nut
Maybe that helps. I think I saw some other script also, but I can't find it right now.