I dispute the Serious Sam claim. The LucasArts iMUSE system was doing things like that years before. Even among fps games, the first Dark Forces game used it.
It's also possible they just didn't know. LucasArts didn't push the system all that much in their PR. You'll see it in some bullet points on the retail boxes, and articles of the time might make a passing reference to it. It was quite a remarkable system for the time and they were very low key about it.