The original QSound hardware was famous for being a "3D" audio processor—panning sounds left, right, and center to create a sense of space. The HLE implementation accurately recreates this stereo panning and spatial effects, which is vital for the experience of games like Street Fighter III: 3rd Strike .

To understand why qsound-hle.zip exists, we have to look at how MAME handles sound chips:

To fix this, early emulators did the obvious thing: they extracted the real microcode from a physical QSound chip (a process called "dumping") and stored it in a file. That file was qsound.zip . It contained the literal, copyrighted code written by Capcom’s engineers. Legally, distributing this file was a minefield. While MAME’s core code was open-source, the qsound.zip ROM was Capcom’s intellectual property. If you wanted to emulate CPS-2 legally, you were stuck.