A good producer nearly always has ideas that one or more of a band will hate......... Especialy the main writer of whatever song is being disected........
Glyn Johns and Tom Dowd are rightfully huge names in the field, and it was a big feather in NMA's cap to work with them at the time. It's not just about money, those two names get to choose who they work with, because they have worked on HUGELY popular records over decades......... They undoubtaby have an ear for good songs and good studio sounds. Both those lp's SOUND as good now as they did then to me. They haven't aged particularly, because the producers have a much longer track record than "names" of the 80's production style. They go back to late 60's/early 70's lp's, some REALLY GOOD ONES at that!......
I think NMA's Northern Soul/Folk heritage of song writing helped take them some where else sonically, than alot other's 80's Alt' heroes........ Dunno, just my opinion.
Impurity bears lots of halmarks lifted from the two previous lp's, with other bits thrown in. I think Rob n Justin learned alot from the experience of working with the 2 names mentioned. Rob definately had a great ear, Justin sez he's half deaf, but I don't believe that affects how you FEEL a song. If you know what I mean? I think he hears way more than he lets on! =)
Being a producer isn't just the sound of the record anyway, it's the structure of songs aswell...... Just have a look at the Classic Albums dvd series. They are hugely interesting if you are involved on writing music. I love them. There's lots to learn from stuff like that fer my money.