DLSMusicDevice is a built-in AU SoundFont player for the Mac OS. It's listed under the Apple Audio Units.
Download some SoundFonts (piano is default) here:Once you have your SoundFonts, place them in the following path:
HD/Library/Audio/Sounds/Banks/
If you happen to download any compressed SoundFonts (sfArk) files, you can decompress them with sfArk.