My friend and provider of music Buckethead has recently being fighting with z80 coding on the CPC and produce two demos in a short period. These were posted on Pouet and went unnoticed here, so I'll post the links.
Starbobs464
https://www.pouet.net/prod.php?which=85633
Dash 4 in 1
https://www.pouet.net/prod.php?which=86965
https://vimeo.com/462546093