There are some excellent books about how VSTi works for example on Kindle https://www.amazon.com.au/How-Make-Noise-Analog-Synthesis-ebook/dp/B005SGCD6A/ref=sr_1_1?ie=UTF8&qid=1543096082&sr=8-1&keywords=How+to+make+a+noise

There are three books in the series
How to make a Noise: Analog Synthesis.
How to Make a Noise: Frequency Modulation Synthesis.
How to Make a Noise: Sample Based Synthesis.

All by Simon Cann. They cost about $3 each and about 130 pages in each. By the time you get through these books you’ll have a good working knowledge of how the various forms of synthesis are created and applied. This will in turn give you a good knowledge on VTSi stuff.

MIDI is a different story

They are worth a read IMHO

Tony

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