If you have a repo available, I can clone it and show you what I mean. Please see Requesting Help, and considering making a small project to share with the content you are talking about (include your front matter). 
I am not certain what you mean, but all the taxonomies are “flat” in Hugo. To generate all those extra feeds you’ll have to do some extra work to associate terms to each other and then the templates for them all. Whereas if you include the following in your config, your audioformats should create the feeds you are looking for (presuming you are using YAML, please see configuring taxonomies):
taxonomies:
audioformat: audioformats
I suggest sharing your repo, so we can see what you’ve got going.