Pete of Casperelectronics.com recently updated his website to include a blog. The very latest entry is a nice virtually step by step guide to circuit bending a Barbie Karaoke tape machine with echo effect. These rather pink devices are readily available on eBay for cheap. The resulting sounds are devastating to say the least. The tape motor control mod is also posted and I am sure can be applied to any tape device. The key appears to be the use of a voltage regulator, which outputs a steady voltage without effecting the rest of circuitry too much.