After a lot of headache-inducing matrix maths (more so than the flying pigs of last week), I have moved a few steps further in my mini game engine development.
The engine now allows for a parent-child relationship of 3D entities, as well as 3D positional sound through DirectSound which can be attached to any entity.
What this has resulted in is a 3D flying bee with attached flapping wings that can be moved around the game environment. As the bee swoops by the (tracking) camera, the sound of flapping wings can be heard as it approaches and flies off into the distance.
Again, not ground-breaking, but the underlying technology has meant that the engine is becoming more extensible and hence useful, as well as improving my understanding of 3D algorithms.