Thanks. So sound cards ended up buying dual purpose interface adapter cards (for CD ROM), and sound cards.
I never really needed (or maybe didn't remember)to understand that when I got my first CD ROM drive. Maybe my dad did, or we had a pre-built thing that just worked.
@JTS@thomasfuchs Speaking of playing music: the small white 4-pin connector above the “Wave Blaster upgrade option” connector was for connecting the CD-ROM drive’s analog audio output. Many CD drives couldn’t accurately extract digital audio over IDE/SCSI/whatever without clever software such as “cdparanoia”.
@bk1e@JTS Sound cards from the era are pretty interesting because there's so many things you can attach to them, both internally and externally.
Almost a spiritual successor to multi-I/O cards from the 80s (RTC, floppy, floppy+hard disk controller, serial/parallel) which got integrated into motherboards.