Hm, yes, sounds very interesting, BUT, I've not got any sort of CPC so I assume it would be no use to me.
I play around with quite a bit of midi stuff, PC based. Various pieces of software, incl some I've written myself, to play and manipulate midi files/music. Various devices attached to one of my old PCs, connected via a Roland LAPC-I card. Recently finally got around to trying a bit of 'virtual synth' stuff, using soundfonts, which bypasses the sound modules I've got. Interesting, but I'm feeling the older stuff sounds more natural.
I've got an old PC (DOS) version of 'Band-in-a-Box' which is getting into the same sort of field as the system referred to here, although BiaB does not 'compose' any melody, just the backing stuff based on a melody, or chords for the melody, that is entered. Again, the actual sounds are generated via midi, and would be dependant on external units. Or the Roland card mentioned (which is in effect a MT-32 box on a card, with MPU interface added). Got a Yamaha MU90r and a Korg NS5R connected up here.
Do keep thinking about trying to get a midi interface built for my PCW? Got a possible circuit diagram. But, the old PC does quite OK, and the Roland card will never work with the PCW, so prob no point?
Geoff