When I cycled from London to Scotland for the G8 Summit in 2005 we towed a custom built soundsystem behind a tandem and it made a huge difference to the ride. Since then Pedals as it became known has been in action in London on a number of events and loads of people have asked how to build something like it.
There are two basic types of situation I am interested in. First there are events like Critical Mass where you want to provide music and perhaps a PA system while on the move and battery power is probably the only option. The second is where you want an easily portable system that can be set up and run away from mains power. Of course you could take a standard mains powered system and a generator, but generators are noisy, smelly and often unacceptable on general principle. Again you need a battery, but you have the option of keeping it topped up with human powered pedal generators and possibly solar or wind power. In either case, in order to be able to play for as long and as loud as you need on limited power you will need to concentrate on achieving high efficiency. Weight considerations are important too, and designing a system to play on the move presents some additional challenges.
www.zenatode.org.uk Ian Gregory 2010