HST was actually what USRobotics called their implementation of 9.6k. The others two were Hayes and Telebit Trailblazer. V.32 came after the ITU realized it had to standardize stuff that was already out there. Same with error correction and compression: We had stuff from Microcom called MNP before the ITU standardized V.42/V.42bis. Most people used HST however, because it was considered the most reliable with international phone calls, especially on those shitty satellite links.
Funny thing is, all PC cards back then were 8 bit ISA on the I/O side, but the Soundblaster was actually the first mass market card to have an actual DAC so you could play back PCM samples in addition to the AdLib sound. The AdLib itself was just a cheap FM synthesizer chip from Yamaha and couldn't play back sound samples. Still better than those PC beeps, though.
That was in the 70ies and way before my time. I actually learned programming on the C64.