It reminded me of Operation Neptune (1991): each level starts with just one channel, probably percussion, and as you progress through the rooms it adds and removes more channels or sometimes switches to a different section of music. It is unfortunately all sharp cuts, no attempts at smoothing or timing instrument entry and exit. A couple of samples: https://www.youtube.com/watch?v=S0LNaatyoQk is an hour of gameplay revelling in “the dynamic and sometimes beautiful music of Operation Neptune” using a Roland MT-32 MIDI synthesiser; and https://www.youtube.com/watch?v=wPxEdQ4wx9s&list=PL3FC048B13... is the PCM files used on some platforms (if you want to compare that track with the MT-32, it starts at 28 minutes).