I was thinking about this out on my ride yesterday. As I said earlier, I use one earbud, but only when I'm on a path - it's a rail-to-trail path - incredibly straight, flat, and boring - especially when I'm doing centuries on it. The music keeps me motivated and keeps the pace up. I know that people argue that on the road you need to be focused, and I fully agree. But, yesterday, out on the road, without music, I got so lost in my thoughts that I realized I was paying no attention at all to the road. A pothole caught my attention, and I realized I had drifted far out into the lane. When I'm on the path, with music, my focus stays on the path ahead - the music actually keeps my mind right in the moment. Just my two pennies...