MacBook Air will not output sound to Denon receiver correctly

I connected my Air via HDMI to input on Denon Home theatre. trying to use the speakers. Apple media will not play once the Denon or any other device connected to Air is selected in Setting/Sounds/output. Apple TV visual speeds up and stops, and will not restart. Music speeds up and continues playing at 10X speed, very quietly. If sound is switched back to Mac Air speakers, then media will play, albeit only through the the Macair speakers.

[Re-Titled by Moderator]