PC speaker:
- 8088 mph demo: https://www.youtube.com/watch?v=yHXx3orN35Y
- Area 5150 demo: https://www.youtube.com/watch?v=fWDxdoRTZPc
- Stormlord (game, 1989): https://www.youtube.com/watch?v=lmDJt1etzRE (unfortunately doesn't keep intro screen around for long)
- A nice video explaining PC speaker with examples (also features Chronos from ZX Spectrum): https://www.youtube.com/watch?v=jD4m9JvLy2Y