G'day again Jon W,

I would make a pedantic point and say that REAL Gaffer tape is not duct tape, but the (usually) silver-coloured cloth tape sold at mind-boggling price by movie supply houses and possessing legendary powers of adhesion. No musician uses this grade of tape because:

1/ No musician can afford it,

2/ The rolls are too small (as well as too pricey),

3/ Venue owners like you to successfully remove tape at the end of the gig!

Regard(les)s,

Bob Bolton