The domain has a CORS restriction which disallows XMLHTTPRequests (required by the Web Audio API used in Safari) to play the audio. To fix this specific issue, you would need to adjust the headers sent by the server.
An easier workaround is to use an earlier implementation of audio for the web that can bypass this restriction. Remove the audio element from Hype, and use a standard embed set to autoplay:
<audio id="holidayaudio" width="1" controls="" autoplay="" preload="auto">
<source src="https://www-tc.pbs.org/holiday/2016/pbs_holiday_card_2016-C.hyperesources/END_END_0111_00101_Jingle_Bells__a__APM.mp3" type="audio/mpeg"></audio>
This audio element needs to be embedded in a rectangle, and can be moved off scene.
Here's more ways to control audio ( you would target the
holidayaudio element ID set above in your case)