Watch the The Clock online guitar lesson by Angus Clark from Essentials: Rock Rhythm Unplugged
Part of the audition process for the Trans-Siberian Orchestra involved playing a tune called "Old City Bar", which is played on acoustic guitar. The album version has a lot of overdubs and so forth, so when it came time to learn it I had to investigate what the current guitar player was doing for the live version. When I talked to him about it he described it as a clock that just keeps ticking along. That's what this example is based on.