Machine learning in audio? What are recommended books or online courses that are mostly helpful to someone wanting to delve into machine learning specifically in audio? 

Or is the learning path mostly the same as for any other machine learning field?
I think that resources about speech processing would be a good introduction to audio files manipulation for machine learning in general.

For a broader introduction to audio,
Machine Learning for Audio, Image and Video Analysis: Theory and Applications, Reviews
Book by Alessandro Vinciarelli and Francesco Camastra could be a good read.

Also, check out some blogs like this one: https://www.analyticsvidhya.com/blog/2018/01/10-audio-processing-projects-applications/ (as you mention deep learning in the tags) that can give a good introduction with some hands-on experience.