What are possible front ends for a java audio library?

I have a friend that has been dabbling with programming, and is interested making use of some functionality in a Java library that I wrote for mixing and playing back audio files.

I’m trying to brainstorm on some options for GUI building for him.

I don’t think he wants to try and tackle Swing (main thing I’ve used for the little apps I’ve made), but he seems somewhat interested in JavaFX. He has a bit of experience with Python, so JPython is another real possibility, I assume. I’ve never actually linked JPython and Java in a single program before though. Is it just a matter of importing libraries, that sort of thing?

He is also intrigued by JQuery/HTML5, but I am not seeing a clear path to connecting from there to functions presented in a Java .jar file without going through some very high latency steps. Perhaps the only way that might work as a front end is if the Java .jar file is converted to Android or JavaScript? I’m not clear if these languages are fast enough to handle audio processing at a reasonable latency.

Or am I mistaken, and if I convert the Java to Android, HTML5/JQuery is not an option, but instead Android’s own GUI language would be used?