Mashup by me. EDIT: Damn 2 years later and this track is still getting likes, thanks everyone!
Here's some other BM x SCP mashups I made:
https://soundcloud.com/thepeculiarorange/black-mesa-x-scp-foundation-theme-2
https://soundcloud.com/thepeculiarorange/black-mesa-xen-x-scp-foundation-theme
Songs Used:
Joel Nielsen - Blast Pit 3 [Black Mesa Soundtrack]
Ajoura - SCP Foundation Theme [Used in SCP: Secret Laboratory]

Black Mesa Blast Pit 3 x SCP Foundation Theme (Joel Nielsen x Ajoura)

Guess I should make some more stuff here soon eh?

Black Mesa Blast Pit 3 x SCP Foundation Theme (Joel Nielsen x Ajoura)

The Peculiar Orange