Did some rather cool things with a DSP56k chip, and developed a visual programming system for it like a modular synthesiser in Smalltalk/V. Other systems too.
|VTrainer C, C++ MFC|
We use a DAW based on Reaper with a few bits of mostly DIY gear and we use several VSTs. Reaper has a built in system, JS Script, to actually develop your own "VSTs". I would call it a rapid prototyping system, where you focus on the core of a VST. SynthEDIT could also be used, in a similar way to my Smalltalk/V system all those years ago.
The really interesting part of commercial development always seems so small compared with all the house keeping that has to be done. And on going support may not be simple either.
JUCE is the framework for cross platform C++ VST development for a commercial release. It seems to be a decent platform.
|Juce C++ VST Project|
I was involved with getting the Australian QuickBooks Accounting products product to work on VISTA when that came out. An incredibly tedious task.
Compared to that, VST development is rather simple.....
Contact as at Art & Technology.