Is the answer to 12A really motets? I ask because the dictionary definition doesn't really tie up with the clue. I loved reading the Netibiza dialogues, you guys really seem to know each other well. How long has this been going on? As they say in the song.
Whilst dictionary definitions aren't worded precisely in line with this clue, I think the answer is motets, as nothing else appears to fit the pattern.
The friendly banter .. (although not encouraged by Editor), can make the joint solving of crosswords etc. so much more enjoyable.