The development of custom DSP. The Cube had its own powerful DSP processor which could process sound in programmable ways, rather than simply playing an 8-bit sample or two.
It was the direct ancestor of today's VST/AU/AAX/etc synth and FX plugin market.
AFAIR, it was a stock Motorola DSP. The only that was odd about it was that it was mounted on the motherboard. You could (and I did) get access that sort of DSP through daughterboards before the Cube, but NeXT took the step of saying "this ought to be a part of the computer itself".
I really disagree about it as a direct ancestor of the contemporary plugin API. These have always run on the host CPU, not dedicated DSP chips (excluding of course Digidesign's original ProTools model, but that was DSP farm rather than just a chip).
And the sort of DSP that was being done on the Cube DSP was being done before the Cube too.
It was the ancestor in the sense that the DSP features were part of the OS and not a bolted-on add-on with non-standard drivers. And also in the sense that you now had an off-the-shelf machine that could do non-trivial real-time synthesis and processing.
When NeXT was folded back into Apple, the audio classes eventually became (more or less) the AUs in MacOS.
An abstraction layer made it possible to run natively, or on internal DSP, or on external DSP. Aside from Digi, Waves, Universal Audio, TC Electronic, and Focusrite all made external processors that used the AU/VST interface. (UA still do, although recently they - at last - also started offering native versions of some of their plugins.)
>I really disagree about it as a direct ancestor of the contemporary plugin API. These have always run on the host CPU, not dedicated DSP chips (excluding of course Digidesign's original ProTools model, but that was DSP farm rather than just a chip).
That's like saying "computing in the 80s was all about the home computer market, if we exclude the PC". ProTools was the biggest name (and quite close to a monopoly for pros at the time).
But it didn't put the DSP inside the computer, which is what made the NeXTcube interesting.
ProTools had a separate box that had the DSP farm in it. There was nothing particular unique about that (at the time) (though running a DAW on it was definitely novel when they did it).
There were many things going on at the time. Digidesign made the Sound Accelerator boards for Mac and Atari in 1988 or so? Roughly contemporary to this. I don't remember the exact year, but I think the first instance of commercial 3rd party plug-ins for a software platform is Waves's dynamics plug-ins for Digi's Sound Designer editor. These ran (non-realtime!) on the 56k DSP on Digi's expansion card for Mac (I don't know if the plug-ins were available for Atari).
It was the direct ancestor of today's VST/AU/AAX/etc synth and FX plugin market.