I recently (over the last 2 years) became more aquatinted with the cli. And after compiling a number of open source sample packs (CardOne, SuperDirt, etc…) I was left with lots of non .wav files in several sample directories.
find . -type f ! -iname '*.wav' -delete
^^^was my friend. Pretty basic stuff, but I wish I would have been more willing to learn this a while back.
p.s. -iname because for whatever reason half the wav files were all caps.
p.p.s. Can’t wait to make use of id3mtag. Last month I discovered my old college external hard drive which barely works but I was able to scrape old data from. All my mp3s no longer have any metadata other than decent folder organization and file names.