Is there any way to programatically capture the audio being played from a webpage using html5, jS, or something else and create a mp3/wav file out of it? I know of the web a
You can use the Web Audio API to record the output of any Web Audio node, not just microphone input. If the webpage you want to record audio from is using the Web Audio API to generate sound, then you can definitely use the Web Audio API to record it (check out Recorder.js).
If the sound is being played from html elements, you can turn it into a Web Audio node and record it. Check this out: http://updates.html5rocks.com/2012/02/HTML5-audio-and-the-Web-Audio-API-are-BFFs