That was a super useful breadcrumb to follow.  I didn't know about the SDKs.  On Macintosh Garden, I found the Apple Developer Connection 1996, and the December issue (reference library) contains article #20 which contains an article on how to write a sound output component, along with some sample code.

Note that I had to open this on an old Intel MacBook Pro running Mojave; my usual M1 MacBook Pro on Ventura won't mount HFS.  Anybody know a way around this, for CD images and DMGs?