Reading raw wave data in JS/HTML5?

I'm working on a music synthesizer/sequencer app in JS/HTML5. One of the things I want to do is to be able to play samples from wave files. I'd like to be able to access the raw data contained in the files (individual sample values). There doesn't seem to be a way to do this with the HTML5 audio API, as far as I can tell.

Would the HTML5 file API allow me to access the raw data contained in files at a given URL? Would I need special permission from the user to do this? I'm also wondering if this would work with local files for local testing of my app.