What sound format does the sequencer support?

I’m at the point where it’s time to apply sounds to my sequence. I thought this would be the easy part :\

So I’m in my sequencer and everything is in there 'cep the sounds. I click Add, and the menu clearly stipulates “Sound (Wav)”

I click that, expecting my Wav files to be nicely listed.

The file selector window opens, but no Wavs are shown. The button at the top says “Select Audio (RAM)”

Aren’t RAM files not even an actual media file? I thought they were a real audio metafile that link to a sound resource at a URL. If I try select WAV or MP3 files manually by typing in their names, Blender tells me it’s an unsupported file type.