Most of the tracks for The Grim Roper have vocals and guitar recorded in separate recordings. But a few of the tracks had vocal and guitar recorded at the same time, so the guitar track contains some vocals and the vocal track contains some guitar. And on a cassette tape 25 years ago, this wasn't a very noticeable problem.
This is not so true when mixing for CD. Because the vocal signal arrived at the guitar mic later than it arrived at the vocal mic, there's an annoying phase problem which causes the vocal to sound hollow. And the louder I was singing on a song, the larger the phasing problem is, because there's more vocal in the guitar track to interfere with the vocal on the vocal track.
In what should not be a great surprise, the interference is the greatest on "Space Is Dark". Yes, space is dark and I was loud. *sigh* In space, everything could hear me sing.
The good news is that there are tools that you can use to fix phase problems like this. I auditioned one of them tonight, the Little Labs IBP.
And happily, it seems to make things better.
Also happily, I had a $50 off coupon.
So I now have yet another plug-in sitting in the toolkit.