Sony's stopped updating their original NetMD software for transferring music files from a computer to a MD recorder about the same time they stopped making the recorders themselves. But fear not, intrepid MD Warriors! Several very industrious devotees have stepped up and created software that is—for all intents and purposes—better than Sony's original.
One of them is PlatinumMD:
I couldn't get this working the first time I tried it, but apparently the author released an update that works with the M-series Macs, and now it works just fine. The downside is that a bunch of ancillary code must be installed via HomeBrew in order for this to work at all, and not being at all familiar with HomeBrew, I really didn't have a clue what I was doing. But it worked…
Another one is WebMD Pro (requires the Chrome browser, which I loathe). Fortunately there is also a standalone application, electronwmd that has native MacOS support built-in:
Until I got Platinum MD working, this was my go-to NetMD application, and it's astoundingly simple interface is what still brings me back when I need to do some quick-and-dirty editing (or verify that what I did in PlatinumMD actually worked).
Finally, today I discovered NetMDWizard, a nifty application that lets you directly transfer/encode music tracks from CD to MD:
When recording, the absolute best quality you can get is a direct optical cable connection between your CD player and your MD deck. That being said, the whole NetMD ecosystem produces results that I (and many others) are hard pressed to find fault with. For all intents, the MD recordings sound as good as the originals. Yeah, yeah, I know…converting from one lossy codec to another will produce undesirable artifacts, but except for some minor sibilance heard with certain percussive instruments—or strident overtones heard with certain electronic compositions (and then only when recording in SP2 mode)—the quality certainly is good enough that unless you have the hearing of an 18-year-old, you'll never notice any degradation.