While looking for info on Soundtrakker I ran across this excellent article:
https://64nops.wordpress.com/2017/12/29/les-logiciels-de-composition-musicale-sur-cpc/ (https://64nops.wordpress.com/2017/12/29/les-logiciels-de-composition-musicale-sur-cpc/)
For English speakers Google translate does a fine job :)