Aggressive algorithmic randomisation of synthesis parameters.
On some level these pieces were made by the named author, but in other respects, the key elements are contained in the synthesis algorithms themselves: the specific synthesis methods, routings, timbres, dynamics, behaviours, etc. are the significant material. That, and the musical and cultural associations conjured by these specific synth sounds.
Martin LΓΌders' excellent Roland JX-8P emulation is used extensively:
https://sites.google.com/site/mlvst0/pg8x-2
As well as the Yamaha DX7 (Dexed) and Oberheim OB-X (OB-XD) clones to a lesser extent.