Half-Life 2 soundtrack

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Kelly Bailey composed numerous short pieces of original incidental music that are interspersed throughout Half-Life 2. Also, several tracks from the Half-Life soundtrack were re-titled and carried over, some of them remixed. Energetic techno tracks tend to back significant battles. Atmospheric synthesizer pieces enhance key plot and exploration moments and reinforce feelings of adventure, isolation, or melancholy in the player.

The limited-edition Half-Life 2 "Gold" package included, among other exclusive extras, a CD soundtrack. Although the CD contains several exclusive tracks, it does not include all of the music released with the game. Using an appropriate program, it is possible to extract all audio tracks heard in-game from the "source sounds.gcf" archive file. Tracks 44–56 in the list below were not released on the CD and can be obtained by this method. The soundtrack (save the CD version of tracks 1 and 34) was also included in the game directory of both the full and demo Audiosurf releases on Steam.

In September 24th, 2014, Valve released the soundtrack for Half-Life 2 and its Episodes as a free DLC available to anyone who owned the games on Steam.

Track listing

Track	Description	Location played
"Hazardous Environments”	The most iconic track, this is now the signature theme of Valve Corporation. Presented in the game files as "HL1_song11".	At the titles, a section of the track can be heard when putting on the HEV suit for the first time in the game.
“CP Violation”	Fast paced action music. Presented in the game files as "HL2_song20_submix0". While the title ostensibly refers to Civil Protection (CPs), "CP Violation" is also a term in physics that refers to violation of CP-symmetry.	Route Kanal: During Route Kanal, early in the level in a train tunnel that has Gordon moving through passages on the side. Later in the level a remix of the track is played.
“The Innsbruck Experiment”	Refers to the Quantum Teleportation experiment done in 1997, Innsbruck, Austria. "Beam Me Up" For more info on the name. Presented in the game files as "HL2_song4".	Route Kanal: when first fighting MP7 wielding Metrocops. Anticitizen One: when Dog shows off his strength during a fight with Overwatch Soldier. On console versions of The Orange Box, this is played when highlighting Half-Life 2 on the menu. This was the music used throughout the duration of the Half-Life 2 trailer.
“Brane Scan”	Relatively slow paced action music. Continues same beat throughout, with some electronic sounds - however, mainly drums. Presented in the game files as "HL2_song31".	Anticitizen One: leading up to the fight in the plaza containing the Combine generator.
“Dark Energy”	An upbeat song with an industrial feel to it which is consistent with Ravenholm's derelict industrial ocean harbor. Presented in the game files as "HL2_song3".	Highway 17: Played when leaving Shorepoint Base. During the first part of the credits.
“Ravenholm Reprise”	An eerie track that introduces the player to the dark city of Ravenholm. Presented in the game files as "HL2_song7".	"We Don't Go To Ravenholm...": As soon as the level begins, the track begins.
“Pulse Phase”	Consists of a slow drum rhythm with a factory-like ambience in the background. A more simplistic and dark version of the song "Drums and Riffs" from the original Half-Life. Presented in the game files as "HL2_song6".	Follow Freeman: As the player enters the Strider battle just outside the Overwatch Nexus. Dark Energy: When the player is descending in the elevator to face Breen.
“Requiem For Ravenholm”	The "Ravenholm Reprise" track, only shortened and centering around a loud guitar wail. Presented in the game files as "Ravenholm_1".	"We Don't Go To Ravenholm...": After passing through the gate at the end of the courtyard and Father Grigori bids farewell, the song plays. This is commonly not heard because the loading area is right at the other side of the door.
“Probably Not A Problem”	A harrowing track, follows through a strange siren like refrain before ending with a subtle outro. Title refers to a line heard in the test chamber in the original Half-Life. Presented in the game files as "HL2_song33".	Route Kanal: During the Headcrab shelling towards the end of the chapter.
“Calabi-Yau Model”	Not so much dark as very strange, follows through a distorted field of sound effects. Seems to be very anticipatory. Quite eerie. Presented in the game files as "HL2_song30".	Upon entering the Vortigaunt Camp in Sandtraps, as well as the Zombie-infested building near the start of "Follow Freeman!".
“Slow Light”	A very simple but emotional song. Sounds similar to the music when entering Ravenholm, albeit with no background sounds and a longer duration. Presented in the game files as "HL2_song32".	Highway 17: New Little Odessa, after the Gunship has been defeated.
“Apprehension and Evasion”	Fast paced action music. The name is most likely a reference to Gordon's apprehension by Civil Protection and his subsequent escape through which this song is played. Presented in the game files as "HL2_song29".	"A Red Letter Day": While escaping from Civil Protection through the train tracks. Sandtraps: During the night time raid on Nova Prospekt (the bunker raiding section).
“Hunter Down”	Extremely short and dramatic trumpet piece. The track is commonly confused with "Sharp Fear Short", which is a 8 second dramatic track that plays whenever a miniboss is defeated in HL1 - and when the Hunter-Chopper is defeated in Water Hazard. Presented in the game files as "HL2_song28".	In Follow Freeman!, played directly after the last Strider is killed.
“Our Resurrected Teleport”	A calm and relaxing song. Presented in the game files as "HL2_song26".	"A Red Letter Day": The teleporter room in Kleiner's laboratory
“Miscount Detected”	Probably a reference to the chapter Point Insertion, where Overwatch detects a miscount (Freeman) in the apartment building. Presented in the game files as "HL2_song25_Teleporter".	Despite the reference, the track is not used in the game.
“Headhumper”	"Headhumper" is the term Barney uses to describe Headcrabs. Presented in the game files as "HL2_song24_Lamar".	In the Half-Life 2 beta, there is a G-Man sighting, where if Gordon sees him, he books it away from the window, the lights around Gordon flash, and the track plays. It does not appear in the retail version of Half-Life 2.
“Triage At Dawn”	A very earnest track. It is designed to be contrasted with the atmosphere of Ravenholm, once more placing the player in the middle of an uprising, while simultaneously almost mourning the situation - played in tandem with Winston's moans of pain. Presented in the game files as "HL2_song23_SuitSong3".	"We Don't Go To Ravenholm...": At Shorepoint, when the battle in the garage is over.
“Combine Harvester”	A militarist, marching song. It could possibly be a Combine anthem of some kind. The title is a reference to the "combine harvester", a farming machine that harvests grain crops. Presented in the game files as "HL2_song22_CombineTheme3".	The track is not used in the game, although was supposed to be played in the E3 Beta during the Combine military parade.
“Lab Practicum”	Mysterious, similar to "Shadows Fore and Aft". Presented in the game files as "HL2_song2".	Under the bridge in Highway 17. Also plays when returning to Kleiner's Lab during the uprising at the very end of Entanglement.
“Nova Prospekt”	The name, aside from detailing the location it is played, hints at its content (based on what one already knows of the place). Beginning, with the throb of a bass drum, the track whirls through a range of different ambient themes. A subtle refrain from "CP Violation" can be heard at 1:00 at last for around twenty seconds, before dropping to a more dramatic outro. The track is very creepy and unsettling. Gives a hint at what is to be expected later in the level. Presented in the game files as "HL2_song19". Duration: 1:56.	At the start of Nova Prospekt, just as the player enters the prison block.
“Broken Symmetry”	A strangely-placed reflective track, a repetition of two bass chords with a synth pad. A little similar to the "Self Esteem Fund" track from the Portal soundtrack. Presented in the game files as "HL2_song13".	Route Kanal: Upon leaving the sewers.
“LG Orbifold”	Appears at the climatic ending of Freeman's witnessing of The Uprising whilst fighting a multitude of Striders. Lengthy, fast paced action music. Has a few sections throughout. Title is in reference to one of Isaac Kleiner's lines during the Red Letter Day teleport sequence. Presented in the game files as "HL2_song16".	"Follow Freeman!": At the time of arguably the climax of the game whilst fighting a multitude of Striders.
“Kaon”	Medium paced action music, with guitar riff-style voices taking place. Presented in the game files as "HL2_song15".	Follow Freeman!: When fighting the Combine Gunship over the Overwatch Nexus.
“You're Not Supposed to Be Here”	Fast paced, electronic drum'n'bass-infused action music. Suits a City escape. Presented in the game files as "HL2_song14".	Water Hazard: after receiving the mounted gun for the Airboat.
“Suppression Field”	Presented in the game files as "HL2_song17".	Anticitizen One: While meeting Gordon's first rebel squad member of the chapter in the playground.
“Hard Fought”	A fast paced action track with minimum brass instruments. Presented in the game files as "HL2_song12_long".	Anticitizen One: during various fights with Civil Protection, while assaulting a barricade and the underground shoot-out while waiting a hole to be blown open by a rebel.
“Particle Ghost”	An anticipatory track, seems to awaken one from the darkness of Ravenholm. Presented in the game files as "HL2_song1".	Kicks in upon leaving the Ravenholm Mines and into the sniper's nest outside, right before the Fast Zombie appears.
“Shadows Fore and Aft”	Strange & mysterious music. The whirring of Manhack blades and Kleiner's teleporter can be heard in the background. Presented in the game files as "HL2_intro".	Point Insertion: Very beginning of Half-Life 2, during the G-Man's speech.
“Neutrino Trap”	Remixed from Half-Life Soundtrack, previously known as Hurricane Strings. Presented in the game files as "HL1_song9".	Our Benefactors: Upon exiting the sewer tunnel at the base of the Citadel.
“Zero Point Energy Field”	Reused from the song Cavern Ambience from the Half-Life soundtrack. Presented in the game files as "HL1_song6".	Route Kanal: When first entering the sewers after the Hunter-Chopper first attacks.
“Echoes of a Resonance Cascade”	Known also as "Space Ocean" this track seems to have a very intense 'walking the tightrope' feel, and appears extensively at such moments. Presented in the game files as "HL1_song5".	Anticitizen One: Upon entering the underground hazardous liquid cavern with the cars. Our Benefactors: While Freeman is in the prisoner pod, moving through the Citadel.
“Black Mesa Inbound”	An Ambient track. Reasonably dark, but implies a relatively passive and innocent atmosphere. Fits well during the player's first encounter with Dog. Name derived from the first level of Half-Life, in which Gordon is making his way to the Anomalous Materials Lab. Duration: 2m 11s. Presented in the game files as "HL1_song3".	Black Mesa East: The scrapyard where Gordon first receives the Gravity Gun and meets DOG.
“Xen Relay”	A somewhat dark and zapping, spooky string that plays throughout the song. It's known previously as 'Threatening Short' in the Half-Life Soundtrack. Presented in the game files as "HL1_song26".	Dark Energy: Upon reaching the top of the Citadel just before meeting Breen.
“Tracking Device”	A techno song. This is a remix of the song Credits - Closing Theme from Half-Life. Presented in the game files as "HL1_song25_REMIX".	The second credits song.
“Singularity”	Remixed from the Half-Life Soundtrack, previously known as Travel Through Limbo. An atmospheric track consisting of a pumping synth pad and mixed square wave noises. Presented in the game files as "HL1_song24".	This is played upon the viewing of the Nova Prospekt teleporter in Entanglement.
“Dirac Shore”	Reused from the Half-Life Soundtrack, previously known as Dimensionless Deepness. It opens with the sound of water splashing (a possible reference to the track's name). Like most of the ambient soundtrack, it is hard to hear - keeping volume to a minimum - but is somewhat eerie. Its name is most likely a play on Dirac Sea, a "theoretical model of the vacuum as an infinite sea of particles possessing negative energy". Presented in the game files as "HL1_song21".	Entanglement: when entering the flooded basement.
“Escape Array”	Starts with the blast of a distorted electic guitar chord. Comes from the Half-Life song "Electric Guitar Ambiance". Enhances feeling of desolation. Presented in the game files as "HL1_song20".	At the beginning of Black Mesa East, right after the loading screen.
“Negative Pressure”	Reused from the Half-Life soundtrack, previously known as Steam In The Pipes. Presented in the game files as "HL1_song19".	Our Benefactors: At the beginning of Dr. Breen's speech saying, "You have destroyed so much. What is it exactly that you have created?" In addition to Half-Life 2, this song appears (though not on the soundtrack) of Episode One during the elevator sequence in the Citadel.
“Tau-9”	Reused from the Half-Life song "Drums and Riffs" with a minor change at seconds 22 and 23. Presented in the game files as "HL1_song17".	Highway 17, when first reaching the crane.
“Something Secret Steers Us”	A techno-sounding track. Gives off a feel of urgency. Reused from the Half-Life soundtrack, previously known as Nuclear Mission Jam. Presented in the game files as "HL1_song15".	Lighthouse Point during the Dropship attacks in Sandtraps.
“Triple Entanglement”	Remixed from the Half-Life Soundtrack, previously known as Sirens In The Distance. Presented in the game files as "HL1_song14".	Anticitizen One: Upon entering the Zombie infested sewers near the end of the chapter.
“Biozeminade Fragment”	The song tends to be a slightly faster version of 'Alien Shock' from the Half-Life Soundtrack	Wasn't used in the game.
“Lambda Core”	A fast-paced track with a car-chase feel. Its Half-Life name was "Diabolical Adrenaline Guitar", a good indicator of how it sounds. Presented in the game files as "HL1_song10".	Water Hazard, when fleeing from the second Hunter-Chopper, involving drives through large cement pipes.
“Hazardous Environments (Game Mix)”	A much shorter version of Hazardous Environments. Presented in the game files as "HL1_song11".	Immediately upon equipping the HEV Suit.
“Tracking Device (Game Mix)”	A remix of the Half-Life credits song. It is a fast-paced techno song.	In the credits.
“Entanglement”	Nova Prospekt: Upon entering the Combine Wall crushing canyon at end of chapter, just before meeting Alyx. Route Kanal: At the beginning of the chapter, when the player is on the stairs waiting for the train to jump, if the player quick saves and then loads, this track will play. It may be a hint that Valve wanted this track to play on that part, but it was cut. This track started as an ambient sound, that would play continuously when the player was near a Combine Wall. It can be heard in the Half-Life 2 Beta, in the folder hl2\sound\ambient. The .wav file is named wall_ambient_loop2. Presented in the game files as "HL2_song0".	Just when escaping the prison base of Nova Prospekt before chapter Entanglement.
“Pulse Phase (Game Mix)”
“Highway 17”	A very calm and peaceful song. Presented in the game files as "HL2_song8".	Sandtraps: In a house just outside the zombie-infested tunnel, where a few Rollermines also break in an attempt to attack Gordon.
“A Red Letter Day”	The title track of the short level, extremely minimalist, sounds like a distorted choir singing. The track is barely audible, but if one pauses about 5 seconds after entering Kleiner's lab, one will hear it. This is actually a track taken from 1999 video game "Nocturne" where it plays inside the Spookhouse Headquarters. Nocturne's entire soundtrack is public domain, which is why it made its way to several movies and video games, including Half Life 2. Presented in the HL2 game files as "HL2_song10", while in Nocturne's game files it's known as "HQ".	During A Red Letter Day, upon entering Kleiner's lab for the first time.
“Sand Traps”	The entire soundtrack is quite disturbing, with what seems to be short, sharp echoes. Presented in the game files as "HL2_song11".	At the beginning of Sandtraps, when driving through the tunnel full of zombies.
“CP Violation (Remix)”	Medium-fast paced action music. Presented in the game files as "HL2_song20_submix4".	Route Kanal: Upon leaving the pool with a mixer in it, where Civil Protection proceed to roll explosive barrels at the player.
“Train Station 1”	Presented in the game files as "HL2_song26_trainstation1".	Point Insertion: This music plays just outside the City 17 Trainstation, when seeing City 17 for the first time.
“Train Station 2”	Presented in the game files as "HL2_song27_trainstation2".	Point Insertion: Plays when being chased in the rooftops. Follow Freeman: Plays when seeing a dropship from the Overwatch Nexus.
“Intro Stinger”	Short and silent ambient track consisting of mechanical, metal-like sounds. Presented in the game files as "industrial_suspense1".	During the chapter Water Hazard, it is played when the player reaches a bridge where a citizen drops supplies. Inside the Citadel, upon receiving the super-charged Gravity Gun. In Half-Life 2: Episode Two, this track plays in the chapter Riding Shotgun, in the Advisor barn, just before meeting the Advisor.
“Combat Stinger”	Another short ambient track similar in style to the previous one, only significantly louder. Presented in the game files as "industrial_suspense2".	Just before reaching the room with the Strider in the Citadel.
“Radio”	Despite being one of the shortest and most simplistic, it is most probably the darkest track on the soundtrack. It is mostly a strange, discordant sound, as if a multitude of songs were mixed together. Very eerie and disquieting. Ends abruptly, as if a real song were being played. Presented in the game files as "radio1".	Anticitizen One: Just as the TV with the G-Man on it is seen.
"Apprehensive Short"	One of the many short string suspense tracks from Half Life 1 reused in Half Life 2. Presented in the game files as "HL1_stinger_song7".	Before the conversation between Alyx Vance and Eli Vance as his Combine Cell opens.
"Scared Confusion Short"	Presented in the game files as "HL1_stinger_song16".	Sandtraps: When you encounter a sand path with no industrial objects.
"Bass String Short"	Presented in the game files as "HL1_stinger_suspense8".	Route Kanal: Where you meet a dark hallway with two Combine soldiers and two Citizens praying for mercy.
"Dark Piano Short"	Presented in the game files as "HL1_stinger_suspense27".	Route Kanal: When breaking out of the vent and entering a sewer with lots of explosive barrels stacked up.
"Sharp Fear Short"	Presented in the game files as "HL1_stinger_suspense28".	Water Hazard: When defeating the Hunter-Chopper as a mini boss in the game. Sandtraps: When you step on the sand after you passed a large open sand area and an Antlion Guardian spawns up from the sand.

Trivia

• The name Triage at Dawn is a reference to the very situation the player finds himself at the point it is played - Triage of Winston at dawn break.

• "Triage at Dawn" is incorrectly said to be based on the track "Path of Borealis," supposedly from the Half-Life 2 Beta. This is completely incorrect, as there is no such thing as a track titled "Path of Borealis" in the playable Half-Life 2 Beta files or any other leaked files. "Path of Borealis" is actually a remix of "Triage at Dawn" with a remix of "Radio" also overdubbed in the middle and at the end of the track made by DJ Dain, named "That Long Train Ride", the song title being apparently based on a note featured in a map of an early Half-Life 2 journey found in Raising the Bar. It was one day presented by a gamer nicknamed "Black Mantis" on the Half-Life 2 Beta oriented Father Grigori Forums. There he pretended he received the track directly from Valve, which was a lie. After that, the lie was spread to the Facepunch forums. Today many players think "Path of Borealis" is a track from Valve, here crediting it to Kelly Bailey, there to Viktor Antonov, who is not even a composer. Many videos of it can be found on YouTube, crediting it as being from the Half-Life 2 Beta, and fixing that lie now appears to be impossible. The track is also used as the game menu music for the mod Obsidian Conflict, where it is also incorrectly named "Path of Borealis" and incorrectly credited to Antonov in the mp3 tag.

• The title LG Orbifold is a theoretical physics geometry term mentioned by Dr Kleiner while checking teleporter parameters moments before teleporting Alyx.

• The title Zero Point Energy Field is a reference to the "Zero Point Energy Field Manipulater" (Gravity Gun).

• The title Xen Relay is a reference to Dr. Mossman's speech about how they control a Xen Relay.

• The title Tracking Device is possibly an ironic reference to the fact that HECU and Combine have been using the tracking device in Freeman's HEV to easily track and ambush him during the events of Half-Life and Half-Life 2.

• The title Something Secret Steers Us is taken from the Vortigaunt quote "Something secret steers us both. We shall not name it."

• Oddly, even though the song is called Highway 17, the song plays in Sandtraps, which is the chapter after Highway 17.

• If Radio is played backwards, one can slightly hear a woman saying "Gordon, can you hear me? Gordon, can you hear me?" or "G-man, can you hear me? G-man, can you hear me?"

• The name Radio is perhaps derived from the similarity of the sound to an old or out-of-tune radio, and that, with the backwards "Gordon / G-man, can you hear me?" makes an explanation - someone trying to contact Gordon or G-man with a badly prerecorded message (recorded backwards and with the high-pitched tone over it).
• Radio is composed of two samples that come from the 1995 sample library "Cuckooland: Ghost in the Machine" from Zero-G, composed by Ian Sanderson and Simon Mills. The first one is called "Distorted Trumpets", while the second one, whose pitch has been raised, is called "Is that the Door?".

• The second part of Radio ("Is that the door?") can also be heard in the film 28 Days Later (at 00:26), Postal in the Central Park theme, the Max Payne soundtrack (at 24:00) and in Silent Hill: Shattered Memories as a song called "Ice".

• The track "Pulse Phase" is actually a truncated version of "Dark Energy", slowed down by 50%.

• The track "Lab practicum", can also be heard during the G-man's Source engine demo in the E3 2003 tech demo of Half-Life 2.