Great discord where many audio programmers hang out, may be able to answer your specific questions when you get to the more detailed areas. https://www.theaudioprogrammer.com/discord

A blog post about an open source C++ pitch shifting library: https://signalsmith-audio.co.uk/writing/2023/stretch-design/

And accompanying ADC talk: https://www.youtube.com/watch?v=fJUmmcGKZMI