Audio Music Visualizer - Audio Intake

Hello everyone,

I'm attempting to develop a music visualizer, but have run across an issue, audio intake. Given this I would like to execute one of the following options, whichever is more practical.
1.) I would like the application to react to all audio coming through the user's desktop.
2.) I would like the application to react to audio files provided by the user. Meaning they would be prompted to select a folder full of audio files, and each one would be played.

So far I have achieved visualizations effects with audio, but only with audio clips i have attached in the assets folder. Any help with this would be greatly appreciated.

Thanks,
Nick