Music & Sound
The Black Mesa Soundtrack features 30 tracks (50 min. in length) of music created for Black Mesa. It was composed by Joel Nielsen, and was released on September 2, 2012 , two weeks prior the mod release. The soundtrack can be downloaded at the composer's website, or at the Black Mesa homepage.
"After seven years, hundreds of hours and too many song revisions to count, the Black Mesa Soundtrack is finally released. Faced with the impossible task of creating a soundtrack that will pay homage to Half Life 1 and the millions of fans worldwide, I have made production choices that some will most likely question. From a slightly different perspective, I have tried to bring what I feel is the essence of Half Life, to Black Mesa.
I had no prior experience composing soundtracks. Creating the sound effects was a challenge all on its own, but the music was a far greater task than I initially anticipated. Luckily for me, the lengthy development cycle gave me time to learn and experiment with a lot of different ideas.
I wanted to try new musical genres and styles in Black Mesa, while still maintaining a Half Life "feel". A few song re-makes were attempted, but there is no point in re-making something that is already a classic. I know I risk much composing a soundtrack so different, but I am hoping the community will come to like it almost as much as the original." (Joel Nielsen) 
Some early renditions of the Black Mesa Soundtrack:
- WGH Topside: Another early version of We've Got Hostiles, this one being closer to the final mix.
- Blast Pit: Was renamed to Office Complex in the final mix, but was never used in-game.
- On a Rail (Old Track) (2012): An early track for the chapter On A Rail which wasn't used in-game or in the final soundtrack.  However, it still appears in the Bandcamp version of the soundtrack as track 31, named Bonus - On a Rail (Leaked). 
- Black Mesa Teaser Trailer (2006): An early mix of Residue Proscessing with very subtle differences to the final mix. It was featured in the Teaser. "The Black Mesa ModDB teaser trailer in all its high res glory.".
- Surface Tension: An early mix of Surface Tension 1.
- End Credits: An early mix of End Credits Part 2.
- Joel Nielsen replaced most if not all hit sounds 
- The ambient/environment sound folder alone is about 1 GB. 
- Jumping and landing on surfaces sound different for different materials (jumping on a solid metal box will sound different than a hollow box). Many of the foot step sounds are also being replaced.