I watched the Mindset II video first, and it was fine if a little dry, but it wasn't until I saw the first one that I really appreciated what it was all about.

As an aside, in that first video he says it's not clear what the capabilities of the Mindset's sound system is. It occurred to me that if MAME supports the platform then its source code might tell you, so I had a look:

Each channel (second channel optional) is driven by a Intel 8042 microcontroller bit-banging an 8-bit resistor ladder DAC. Whatever support exists, if any, for accelerating synthesis or multiple voices must be contained within its firmware blob.