Title: GarageBand Makes No Sound After Using Java Sound Synth
Once you have used the Java Sound Synthesizer, GarageBand (or MainStage) will not make any sound.
Cause Of Problem:
Unknown. Once you have used the Java Sound Synthesizer, something is changed in the way your machine produces sound, that prevents GarageBand (or MainStage) from making any sound.
Don't use the Java Sound Synthesizer if you intend to use GarageBand (or MainStage). If you terminate the KeyMusician Keyboard (which ends use of Java Sound), and then start GarageBand, it will start working again. Setting the MIDI Output Device drop-box to “(none)” might also be enough to fix it.
Fix Available (in version):