When using the "Open an audio file on your computer (.mp3, .json)", there are a couple of things going on:
One is not able to open an audio file on the computer -- I understand why, so this text should be changed.
If the user picks an invalid file type, such as a .txt, the app gets stuck in the Loading... stage. Validating the file and providing feedback to the user would be better.
When using the "Open an audio file on your computer (.mp3, .json)", there are a couple of things going on:
Not a high priority.