This particular cherry took 7 or 8 bites, never mind the traditional 2. Couldn't make head nor tail of the SIs so just solved what I could cold (quite a few very friendly ways in, I thought) and the fog gradually began to clear. Of the 7 words in the "uncovered instructions" I sorted out the first three OK and had the endgame grid constructed without too much fuss, but my goodness it took me an age to figure out what was going on with words 4-7 and the "fragmented downward note"! Even then I proved to myself (not for the first time) how rubbish I am at Quick Crosswords, before finally limping over the finish line.
Bravo, KGB - very nicely done.