Impressive, bit it'd be even more impressive if they'd actually got it to play that music while it played. AFAIK the Apple II had no sound chip while that sounds like a SID or possibly an AY chip. What it had was similar to what the ZX Spectrum had, and while polyphonic music was written for the machine, it was pretty much tied up trying to generate all the right clicks at the right time to make that work, and wouldn't have anything like the time needed to render a 3D maze at the same time (and I doubt it sounded that good to be honest).
If the Apple II really can load bitmaps off disc at that speed, that's pretty good though, and the graphic design work is very good.