For Halloween Markus Hohmann (DevilMarkus) has released an Amstrad CPC demo : Halloween 2021 4mb Sample, first they are some noises then the music starts later around 2 minutes 40 seconds.

To create the sample here is his method : I'm using a volume table I calculated for the logarithmic conversion 256 volumes down to 16. I also use nibbles for stereo playback (1 byte contains stereo informations). The imported .mp3 is pre-gained to 100db and I use some filters on the imported sample.

The original source is a musical remake of the game Cauldron II by SoundLogic which you can find also on Youtube.