Reddit thread: http://www.reddit.com/r/Besiege/comments/2zy4ye/sodom_stalinorgel_featuring_a_very_serious_mlrs/
Music - Stalinorgel by Sodom
Movement - Arrows
Fire - 1 through 8
Aim - , (comma) and . (period)
Remove cover - R
To use, first remove cover by pressing R for about a second. Then, gently raise the missiles by pressing . (period) and tapping R to release the bottom row.
Now you can aim and fire as you please.
Also, youtube won't allow me to use angle brackets