Solitude. For me, listening seriously to music is like floating down an unexplored river. Not knowing what lies beyond the next bend, but thoroughly enjoying the ride. When I sit down to listen I want to hear the songs which create whatever path my mind (subconscious) is open to explore. I never know what songs I'll play ahead of time other than the first one. The subsequent songs are selected to build upon one another, guiding me down an impromptu path. I want to pursue that path without compromise so it takes me wherever my mind wants (or needs) to go. Thus, company would either intervene, interrupting my path, or be bored/confused/bothered with my selections. I don't select more than one or two songs ahead, allowing my mind (emotions) the freedom to dictate the path as I go along. This is also why my system must be engaging and be able to convey emotion well - I need to connect intimately with the music. It can be very rewarding and cathartic for me.