I am listening to music basically all the time. But I am not a big fan of using headphones while sitting at a table with other people. I understand that it can be helpful at live games but Im alittle oldschool and think its disrespectful.
Live... If the table is quite, however if we have a chatty cathy then I will listen for tells. Sometimes I'll have my earphones in and off or really low so I can hear the conversation and take down mental notes on various players and the hands they played.