[Barry777]

Take a look at your pinch roller - sounds like it has a lot of small cracks. This will make the tape speed (and thus the audio) vary several times per second, resulting in a fluttering effect without upsetting the picture.

A similar effect happens when a Hi-Fi tape is played back with the tracking slightly misadjusted, but there is usually a "fart" sound along with it. The problem you have sounds more like a typically aged and dried-out pinch roller. You can probably still get a new replacement.

The suggestion above about tape edge damage also makes sense. Make sure your VCR isn't actually causing it, as that would make all tapes appear have the problem also (if not the pinch roller). Try playing a tape first in the GE, then another VCR to make sure it still plays in a known good VCR. Not a bad idea to make sure the tape isn't getting curled on the top or bottom from guide posts drifting out of alignment. However, the pinch roller is the strongest suspect in a unit that age.