Probably using these tools:
Unity 3D
Pro tools 9 MP
Sketch up
Bfxr sound generator
Blog post with some tools I used for other LD project:
http://www.ludumdare.com/compo/2012/05/02/micro-world-toolbox/
I’d like to highlight GXSCC - Automatically converts a MIDI to 8-bit chiptune. Just drag and drop your MIDI to this window, then click Authoring to export it.
GXSCC
Good luck and have fun