I have to have some sound in the house pretty much constantly--not for me, but for the dog. She'll bark at the tiniest sound from the neighbors. So I usually turn on a familiar TV show or movie; something I can listen to and follow along without having to really watch or pay attention. Sometimes I'll turn on music and sing along. :) I don't know that really do much thinking or contemplating, though--that's what running and walking time is for.