the best way to play music without deer hearing is withheadphones or earphones. I keep busy with texting my friends that are hunting also.
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If you have kids, then take there gameboys or what ever they have from them and play that.
Volume wise for volume I wouldn't know exacualy but a good way to test it while in your stand is take your headphones off then turn the volume all the way up and cover the ear part with your palm or something (acting as a ear because it does differ from having something there and not). Just turn it down till you can't hear it anymore or till you think the deer wont hear it.