John. to my ears, the chords are not 7ths.

I'm having problems with that abc btw or at least a copy/paste of it.

Convert-o-matic yeilds: No image available -- there's probably a error in the ABC source causing the conversion to fail.

Our site (which doesn't play chords) on a page I sometimes use for testing it does render an image but gives loads of warnings which I don't understand as the seem to point to backshlashes - characters that simply do not exist in your abc.

Skink crashes when I play the melody.

I'll try to get to the bottom of it when I wake up but at the moment, the only thing I have found which I would question is   which appears in a lot of places in the source.