A simple passive speaker for your bicycle using the parts you have lying around. Loud enough to hear on quiet roads. A person with very basic soldering skills should be able to do this; doesn't require any advanced electronics knowhow.I made this because getting up those hills can be easier with some tunes, and I didn't have the cash to buy one of the commercial ones. I really liked this too because it recycled things that weren't being used anyway - go green!