[blovescoffee]

It depends on what programming language you'd like to work in and what exactly processing means to you. Are you interested in audio analysis or writing programs that generate audio like a synthesizer for a DAW? For audio analysis I'd recommend essentia a C++ library with Python bindings. For writing plugins, I'd recommend you take a look at JUCE, which has a decent set of tutorials on their website. You'll notice that C++ is pretty standard in industry because speed and hardware access are important. If JUCE is the sort of thing you're looking for, I'd also recommend the Audio Developer Conference talks on Youtube.

[monadic2]

I've found rust to be very capable as well, if lacking in runtime libraries with native bindings. It's not too difficult to bind into coreaudio and jack, though.

[blovescoffee]

I've actually been doing a bit of research into using Rust for an upcoming project. The JUCE library is just so fully featured that it would be an undue burden to use any other language to write audio software in. Still, I think Rust is an attractive language for this space and there's definitely some talk about expanding libraries for a JUCE alternative.