Bill writes -

Why would you want a USB port in an electric guitar? The answer is simple: convenience. By putting a small USB port and audio codec in a guitar, you’re adding an extra sound board. So when you record, your guitar is digitized locally and the signal is transmitted to your computer over a USB cable. The guitar retains all its standard analog capabilities but outputs to USB as well. Now you can rock steady until your hard drive is full. Here’s how to do it.

How to Build a USB Guitar – Expert Help by PC Magazine – Link.