I've started listening to mellow stuff when I'm on the bike
The 1990's techno stuff has been replaced by 1970's instrumental stuff like this http://www.youtube.com/watch?v=QXoevHyOF_o
i just made a playlist for my ride to school tomorrow:
Echo and the Bunnymen- The Killing Moon
Muse- Time is Running Out
Radiohead- No Surprises
Belle and Sebastian- Electronic Renaissance
Misfits- Saturday Night
Joy Division- Love Will Tear Us Apart
The Jesus and Mary Chain- Taste of Cindy
Cocteau Twins- Lorelei
Arcade Fire- The Well and the Lighthouse
Built to Spill- Else
Pains of Being Pure at Heart- This Love is Fucking Right
Galaxie 500- Temperature's Rising
The Brian Jonestown Massacre- (David Bowie I Love You) Since I Was Six
Pavement- Grave Architecture
The Church- Under The Milky Way
the playlist is kind of random but it has a semi-somber vibe to it. it's exactly what i feel like cycling to lately.
I never would suggest my tests were scientific. I merely checked the time that I could hear a car versus how long it took to get to me and every time was over a minute (with the current levels of fatigue, hydration, mental state, etc) -- at least a mile behind me. If I felt especially fatigued or unable to concentrate, I wouldn't have listened to music or audio books. I also know that I don't pay attention to music and other things that I listen to. My primary focus was riding my bicycle and I payed attention to the road and listening for cars. I can't listen to podcasts unless I give them my full attention or I get nothing out of them. I can accidentally listen to a song on single repeat for over an hour before I notice if I am doing something else. So with the time between when I'd hear a car and my ability to tune out things on the radio taken together, I felt comfortable wearing a single earbud. I would never wear dual earbuds.
I would never listen to music or other things while riding in traffic like in a city or heavily driven road. But in Kansas where I could see the cars coming for miles and could hear them for over a minute, and they were only coming by about 5-10 cars/trucks per hour, often with a decent sized shoulder, I felt comfortable. On the GAP and C&O which is a bike path and I didn't see any other people most days, I felt comfortable listening to audio books. When I got near Washington DC and there were loads of other runners and cyclists to contend with, I didn't listen to music.
I would say that listening to music while biking under certain conditions is no worse than people listening to their radio while driving a car as a simple distraction from monotony.