Samples and More used in the Soundtracks of Half-Life + Portal.

[VentXekart]

This is a series of videos I watched a while back that had some interesting information on how some of the music and sound effects of Half-Life and Portal were made including the sources of samples used in them as well as the actual instruments themselves. I figured ya'll might appreciate it:
Part 1:

Part 2:

Part 3:

Part 4:

And one more that isn't a part of the series but is still worth noting: