Most of Portal’s soundtrack is non-lyrical ambient music composed by Kelly Bailey and Mike Morasky, somewhat dark and mysterious to match the mood of the environments. The closing credits song, "Still Alive", was written by Jonathan Coulton and sung by Ellen McLain as the GLaDOS character. A brief instrumental version of Still Alive is played in an uptempo Latin style over radios in-game. Wolpaw notes that Coulton was invited to Valve a year before the release of Portal, though it was not yet clear where Coulton would contribute. "Once Kim [Swift] and I met with him, it quickly became apparent that he had the perfect sensibility to write a song for GLaDOS." The use of the song over the closing credits was based on a similar concept from the game God Hand, one of Wolpaw's favorite titles. The song was released as a free downloadable song for the music video game Rock Band on April 1, 2008. The soundtrack for Portal was released in part on The Orange Box Original Soundtrack, which includes both GLaDOS's in-game rendition and Coulton's vocal mix of "Still Alive".
Portal`s soundtrack was released as part of a four-disc retail release, Portal 2: Songs To Test By (Collector's Edition), on October 30, 2012, featuring music from both games.
Using an appropriate program, it is possible to extract all audio tracks heard in-game from the
portal_pak_dir.vpk archive file. On September 24, 2014, the soundtrack was made available as free DLC to all owners of the game on Steam.
* = not present on the The Orange Box Original Soundtrack.
|Orange Box OST #||Game #||Track title||Filename||Time||Level location||Comments|
|*||1||Taste of Blood||
||3:06||Test Chamber 02: Shortly before obtaining the blue Portal Gun.||The title is a reference to GLaDOS' description of the Aperture Science Material Emancipation Grill in Test Chamber 02.|
|*||2||Procedural Jiggle Bone||
||4:34||Also plays in the menu screen.|
|14||3||Self Esteem Fund||
||3:30||The title is a reference to a sentence said by GLaDOS in Test Chamber 15.|
|13||4||Subject Name Here||
||1:44||Test Chamber 11: When riding the Aperture Science Unstationary Scaffold leading to the Dual Portal Device podium.||The title is a reference to a sentence said by GLaDOS in Test Chamber 06.|
|*||5||No Cake For You||
||4:05||Test Chamber 16: When entering the first Ratman den.|
||3:45||Test Chamber 18: When entering the large room full of Aperture Science Sentry Turrets.||The title is a reference to a sentence said by GLaDOS at the end of Test Chamber 16.|
|15||7||4000 Degrees Kelvin||
||1:01||Test Chamber 19: When approaching the fire pit.||Also plays during the second half of the Portal announcement trailer. The title, named incorrectly as Kelvins are not measured in degrees, is a reference to a sentence said by GLaDOS at the end of Test Chamber 19.|
|16||8||Stop What You Are Doing||
||3:57||Escape: After escaping the fire pit.||The title is a reference to a sentence said by GLaDOS in the maintenance areas of Aperture Science.|
||4:21||Escape: Just before and during the first encounter with the Rocket Turret.||The title is a reference to a sentence said by GLaDOS when Chell escapes from the fire pit as well as the Party Escort Bot.|
|17||10||You're Not A Good Person||
||1:22||Escape: During the massive Sentry Turret ambush.||The title is a reference to a sentence said by GLaDOS in the maintenance areas of Aperture Science.|
|18||11||You Can't Escape, You Know||
||6:14||Escape: During the boss fight with GLaDOS.||The title references to a sentence said by GLaDOS in the maintenance areas of Aperture Science, though with a slight change.|
||2:56||Credits||Another version of this song, performed by Jonathan Coulton, is featured in The Orange Box Original Soundtrack.|
|1||12||Still Alive (Aperture Science Radio version)||
- Coulton, Jonathan (October 15, 2007). Portal: The Skinny. Jonathan Coulton's blog. Retrieved on November 1, 2007.
- Walker, John (October 31, 2007). RPS Interview: Valve's Erik Wolpaw. Rock, Paper, Shotgun. Retrieved on October 31, 2007.
- Turi, Tim (2012-09-01). Chell Almost Married A Turret In Portal 2. Game Informer. Retrieved on 2012-09-06.
- Baptiste, Sean (2008-02-21). Valve Party at GDC + Special Preview of an Upcoming DLC Song. Harmonix. Archived from the original on 2008-02-25. Retrieved on 2008-02-21.
- Baptiste, Sean. DLC April 1st! Huge success!. Rockband.com forums. Retrieved on 2008-03-31.
- Faylor, Chris (2008-03-31). 'Still Alive' Hits Rock Band X360 Tomorrow for Free, PlayStation 3 Edition Due Mid-April. Shacknews. Retrieved on 2008-03-31.
- Hinkle, David (2012-09-24). Portal 2: Songs to Test By (Collectors Edition) out on Oct. 30. Joystiq. Retrieved on 2012-09-24.