I've tried the Sound Setup's Sound FX card test on the Sound Blaster Pro. I get a proper center, then left, then right (strike!) on my emulated Sound Blaster device.

It seems to properly handle the commands as the official documentation performs it (except merging the single sample into the main command it seems, simply starting playback on the right sample probably, instead of using a single sample command to perform the alignment).

From what I know Duke3D uses BSWAP only for parsing MIDI data, which is all big-endian. Someone made a patch or a port that gets rid of it and allows the game to work on a 386.