It utilizes four different engines simultaneously—sample playback, analog-style synthesis, FM synthesis, and wavetable synthesis.
Check the LICENSE.md of any public rebuild. Most explicitly state: “No copyrighted material included. You must own Hypersonic 2.” Steinberg - Hypersonic 2.0 -Rebuild SynsoEmu- - AiR
: It used a proprietary engine that could play hundreds of voices without spiking the CPU. Steinberg - Hypersonic 2.0 -Rebuild SynsoEmu- - AiR
: It featured a 1.7GB sample library covering pianos, synths, orchestral strings, and drums. Steinberg - Hypersonic 2.0 -Rebuild SynsoEmu- - AiR