gosh, I had no idea how to replicate spoke twang in print, thanks! I'll wager money that the tool is the issue. if you have one bike, all the nipples should be the same size. get a wrench specifically sized for that, and make sure it's good quality. to check if your nips are brass or AL, take one of your garbage ones and go over it with a file a few times: AL will get shiny, brass will have the nickle wear off and look like, well, brass (think copper/penny/key coloured). brass is tougher than AL, but heavier. I doubt that the weight would be measurable.