OK, this might be it. I used mp3s. Thanks.
Is wav supported?
Wav, but why? As nice as it might be to use lossless audio formats such as wav or flac, I would recommend against it as the file-sizes are massive compared to mp3/ogg/opus file formats - besides your average ordinary person isn't going to be able to tell the difference between a wav file or a 320k mp3 file or an ogg file set to 100% quality.
I highly recommend sticking to ogg or opus because they are smaller in file-size & because as I already mentioned, they are open-container / open-source formats & they just happen to be the file types that VS supports since mp3 was sort of unofficially dropped in 4.x.