The audio compression here used requires the latest version of Quicktime. If you see the Quicktime sound bar, and it appears to play, but you hear no music, it's not that your sound is turned off-- rather, you have an old version of Quicktime (version 2 or 3). Simply click below to download the free Quicktime 4 plug-in, and all will work fine. (Audio compression technology has improved tremendously in just the last couple of years, so the download is worth the bother-- you'll be amazed at the fidelity of these small sound files.)
Technical note: once the download is complete, you'll need to doubleclick the resulting file. The installer will then do everything else for you. Enjoy!