I do like detailed explanations of a project, and i prefer to be in video. That is why my project videos are way too long (for which i have heard some complains). Here is another detailed video from Nerdkits, who made a xylophone from a scratch. They explain very basic concepts of magnetism, and then they contract the solenoids (electromagnets) that will be used to hit the bars. After doing some research, they found an old book with the name "The Theory of Sound, Volume 1" by Lord Rayleigh, in which they found the formulas to calculate the physical dimensions of the aluminum bars that they will use to make the sounds. They also explained how the SIPO shift registers (Serial In Serial Out) work, and how to interface them with their ATmega168 microcontroller. An excellent project with excellent presentation. Check out their page.