Terje

The guitar actually sounds in both the treble and bass clefs, but it's bumped up an octave on the page so that it can all fit into just the treble clef. As is the male voice most of the time. Bass is usually written an octave too high as well, which still leaves it in bass clef but makes it easier to read.

To confuse things you'll see it pretty often in writing that they separate the clefs at other points than middle C...