How do I prevent iMessage from converting high-quality .wav files to low-quality .m4a files?

For years, I've been using iMessage to share high-quality music files and video files via iMessage. It was great, I could use my Mac and send a file to a singer. She could hear it on her phone, without compression. At some point, one of the updates changed what iMessage does with a 24-bit .wav file. It changes it into a .m4a file. I haven't seen any setting where I can disable this. I know that there are other apps I can use for sharing, but iMessage has been so easy and convenient to use. Does anyone have any idea how to fix this?

[Re-Titled by Moderator]