I recently discovered that the latest version of Sun's JRE (v.1.5.0_02) no longer contains midi soundbank files, which happen to be required by my ear trainer. So, if you're using this latest version, you'll need to download and then copy the midi files to your JRE installation. This is an absurd requirement, but alas, Sun's own midi demo no longer works either (without the extra download), so perhaps they'll get wise and rectify things in the next version of their JRE.
If you are using the latest version of the JRE and/or if you don't hear any sound from the ear trainer, please download the midi soundbanks. Any of the three options on that page should work (I tested both the "midsize" and "deluxe" versions). Once you download, unzip and copy the file into your JRE location as mentioned by the installation instructions on that page. In my case, I had to create the "audio" directory and copy the file here: C:\Program Files\Java\jre1.5.0_02\lib\audio
Right about now, you're probably asking yourself, why didn't he just build the ear trainer in Flash? Well, until this ridiculous turn of events, the primary benefit to using Java was the fact that I could use midi instead of wav files for playing sounds. And look how that turned out! *sigh*
Will I redo my ear trainer in Flash? Maybe. I guess it all depends on the next version of Sun's JRE. If it has the same issues as the current version, I'll seriously consider a Flash rewrite. It's painful to think about that, though, when considering all of the work that went into the current version...
And, no. This isn't an April Fool's joke.