For a long time i had not sound in Firefox on Sites using Java (hobnox.com, runescape.com)
I tested the Javasound localy withe the JavaSoundDemo:
and i worked flawlessly.
I had to activate the OSS Sequencer API in the Kernel under:
Device Drivers/Sound/Advanced Linux Sound Architecture/
So even modern sites still use and need the OSS API, good to know :)